Acquired immunodeficiency syndrome (AIDS) is a chronic, potentially life-threatening condition caused by the human immunodeficiency virus (HIV). By damaging your immune system, HIV interferes with your body's ability to fight infection and disease.

Erectile dysfunction (impotence) is the inability to get and keep an erection firm enough for sex. Having erection trouble from time to time isn't necessarily a cause for concern.

frigidity, in psychology, the inability of a woman to attain orgasm during sexual intercourse.

Low sperm count means that the fluid (semen) you ejaculate during an orgasm contains fewer sperm than normal. A low sperm count is also called oligospermia (ol-ih-go-SPUR-me-uh).

Premature ejaculation occurs when a man ejaculates sooner during sexual intercourse than he or his partner would like. Premature ejaculation is a common sexual complaint. Estimates vary, but as many as 1 out of 3 men say they experience this problem at some time.

Syphilis is a bacterial infection usually spread by sexual contact. The disease starts as a painless sore — typically on the genitals, rectum or mouth. Syphilis spreads from person to person via skin or mucous membrane contact with these sores.

Monilia (or Candida) live in small numbers in a healthy vagina, rectum and mouth. When the vagina's hormone and pH balance is disturbed, the organisms multiply and cause infections. Monilial vaginitis tends to appear before menstrual periods and subsides as soon as the period begins.