It is normal for men to experience changes in erectile function, such as taking longer to achieve an erection. When the problem becomes persistent, it can be a sign of a physical or emotional problem.

Although in the past, impotence was commonly believed to be caused by psychological problems, it is now known that up to 90 percent of cases stem from physical problems, usually related to the blood supply of the penis.

Nearly all American men experience occasional impotence, and an estimated 30 million suffer from chronic impotence. But despite its prevalence, the condition is treatable in most cases.

Vasectomy is a permanent male birth control measure and a means of contraception used in many parts of the world.

Male menopause is a condition caused when testosterone levels decrease in aging men.

Peyronie's disease is characterized by a plaque, or hard lump, that forms on the erection tissue of the penis.

Problems with the production and maturation of sperm are the most common causes of male infertility.

Women suffer more frequent and severe symptoms from STDs. Some STDs can cause pelvic inflammatory disease, which can lead to both infertility and ectopic pregnancy.

A lot of us don't realize that chlamydia and other sexually transmitted diseases (STDs) can cause no symptoms, meaning you could have an STD and not know it.

AIDS is caused by the human immunodeficiency virus, which kills or impairs cells of the immune system and progressively destroys the body's ability to fight infections and certain cancers.

What's true and what's not when it comes to AIDS? Here's a look at some common myths surrounding HIV infection and AIDS.

The only safe sex is no sex, most health care providers say. But certain precautions and safe behaviors can minimize a person's risk of contracting a sexually transmitted disease.