Today it's virtually impossible to escape the shameless assault on our sensibilities by drug manufacturer's  promotion of "E.D." medication. When a man finds himself in a situation where he has difficulty  becoming aroused, gaining or maintaining an erection there are a number of possible explanations. These fall into two primary categories: Physiological Could be due to age or poor physical health, such as hypertension, circulatory system, diet, lack of exercise or lack of sleep. Certain powerful medications may also diminish sexual appetite. Low level of Testosterone If the indication is that the problem involves only the penis,  treatments using oral medications, direct injections, implants or vacuum devices often provide positive results. Psychological Depression, financial concerns, work pressure, boredom with routine sex or diminished interest in their partner. Basis of sexual desire The things which people find sexually arousing vary considerably. They may be physical or mental in nature. Most people are sexually aroused by a physical contact from another person, especially if the other person is in an intimate relationship, if the contact is in an erogenous area or if it is accompanied with the anticipation of an imminent sexual activity. In addition, some people may find nudity and pornography sexually arousing, though what aspect different people find arousing will vary. Most heterosexual males are visually stimulated by female nudity or partial nudity, while some heterosexual females are stimulated by the state of romance with their partner. According to the marital and sex therapist, David Schnarch, intimacy, the honest portrayal of the two people joining in the sexual act, may lead to a heightened state of passion in sex, including sexual arousal. Such sexual arousal may not lead to an actual sexual activity, beyond a mental arousal. In a 2004 study at Northwestern University, the female participants (both heterosexual and homosexual women) became sexually aroused when they viewed straight as well as lesbian adult content films. Among the male participants, heterosexual men were turned on by explicit adult films showing only women; gay males were aroused only by films showing men. The study's senior researcher said that women's sexual desire is less rigidly directed toward a particular gender, as compared with men's; and women's desire is more changeable over time. The Libido The libido or sexual desire is key to the process leading to erection. The libido is not located in the groin but in the brain. Physical stimulation of the penis is ineffective in producing an erection without engaging the brain and more specifically the area within the brain responsible for sexual desire. In males the libido is directly related to the level testosterone produced, which varies from individual to individual as well as age. Most men will maintain testosterone levels which are sufficient to desire sex for much of their lives.  Understanding the normal erection process The physiological mechanism which produces an erection is actually counterintuitive. To most the swelling of the penis would indicate a “stiffening of muscle tissue”, when in fact it’s just the opposite. For the penis to become erect its smooth muscle (involuntary) tissue  needs to "relax". At first glance this appears to be entirely illogical. Yet this is a key part of the process, which begins with the release of nitric oxide into the corpora cavernosa (spongy tissue chambers running along the shaft of the penis). The nitric oxide allows this tissue to relax and fill with blood (up to sixteen times its normal capacity). This results in pressure being applied to the veins (leading blood away from the penis), which in effect restricts blood flow out of the penis. The veins are unable to drain blood out of the penis and so the penis becomes rigid and erect. This condition normally keeps this erection firm enough for intercourse. What is erectile dysfunction ("ED")? Erectile dysfunction, sometimes called "impotence", is the repeated inability to achieve or to maintain an erection which is firm enough to allow sexual intercourse. The word "impotence" may also be used to describe other problems that interfere with sexual intercourse and reproduction, such as lack of sexual desire and problems with ejaculation or orgasm. An occasional problem achieving an erection is nothing to worry about, but failure to do so more than 50% of the time at any age may indicate a condition that needs treatment. Diagnosing "ED" Nocturnal penile tumescence test (NPT) The NPT test indicates whether a man is having normal erections during sleep. Most men have 3 to 5 full erections during deep (rapid eye movement, or REM) sleep. Men who do not have erections because of psychological problems can still have erections during deep sleep. Occasionally, some sleep problems or serious depression can prevent these normal nighttime (nocturnal) erections. Self testing A strip of four to six non self-stick postage stamps should be used for each test. The test needs to be done for three nights. For this purpose he should wear brief-type under shorts with a fly opening. This garment will allow the penis to be brought through the fly. The strip of stamps are wrapped snugly around the shaft of the penis. The stamps need to overlap so the overlapped stamp can be moistened to seal the ring. When the stamp has dried, the penis is carefully replaced inside the shorts. The shorts are worn to sleep and help protect the stamps from falling off inadvertently. In the morning, check to see if the stamp ring has been broken along the perforations. If the tearing of the stamps awakens the man during the night, check for an erection and how rigid the erection is. The stamps may be felt as an unusual sensation, but the test should be repeated until three nights of comfortable, uninterrupted sleep is achieved. Evaluating the result Normal: During at least one of the nights, the ring of stamps is broken between any two stamps. If the stamps are broken it may suggest that the erection problem is the result of psychological causes. If the stamps are not broken on any of the 3 nights it may indicate that the erection problem is related to physical conditions or medications. A health care provider should be consulted. The test is not foolproof. It does not indicate many important factors of sexual dysfunction: such as quality, duration or number of erections during the night. Treating "ED" with drugs or mechanical devices A number of heavily advertised pills serve as a substitute for nitric oxide and by boosting its effects. These drugs slow the breakdown of a specific enzyme, prolonging nitric oxide's actions. This allows blood vessels in the penis to expand, which in turn produces an erection as the corpora cavernosa  relaxes and engorges with blood.  In the absence of a "natural" triggering mechanism  (releasing nitric oxide), the ingestion of ED drugs or the artificial vacuum of a penis pump there can be no erection. For some men drugs or mechanical devices are an unavoidable price to pay for achieving a satisfactory erection, but for others the issue may lie elsewhere. Not an aphrodisiac "ED" Drugs are only able to affect the physical causes of erectile dysfunction, not those rooted in the mind. A lack of desire to engage in sexual activity is not always attributable to a physical limitation in a man. I may simply be limited by a physical desire for the long term partner. Side effects of "ED" drugs Unpleasant effects Headache Flushed skin Upset stomach Stuffy nose Urinary tract infection Visual changes such as mild and temporary changes in blue/green colors or increased sensitivity to light. Diarrhea Physical danger and long term harm Should not be used by men with heart conditions whose doctors have warned them not to have sex. Also, patients taking drugs that contain nitrates have been warned not to take ED drugs because of sudden, unsafe drops in blood pressure. Federal health officials are currently investigating reports of blindness in men taking ED drugs. This type of blindness is called NAION, or non-arteritic anterior ischemic optic neuropathy. It can occur in men who are diabetic or have heart disease, the same conditions that can cause impotence and thus lead to ED drug use. Other common side effects Difficulty ejaculating. The penis will not fully relax after ejaculation. Difficulty sleeping Responsibility to satisfy the partner, particularly in long term relationships (marriage) Generally men are sufficiently attracted to a female to produce a potential chain of events leading to an erection. This is not always the case for all men under all circumstances, where there might be a gradual loss of physical interest or passion in the partner. Most relationships begin with physical attraction  and build to a strong emotional bond (love). Over the course of time the physical attraction (excitement) may diminish while the emotional bond actually increases. Love and physical attraction are not always one and the same. While a woman is able to successfully engage intercourse without actual arousal or interest, the same is impossible for a man.  Although it’s possible for a man to satisfy his partner by other means than intercourse, the lack of an erection will still be evident. In the case of those men are not handicapped by a physical debility (such as ED) which inhibits an otherwise desired erection, is it fair to expect that they ingest potentially harmful drugs for the purpose of masking the fact that they are no longer (sufficiently) aroused by their partner?