Sexually transmitted diseases (STDs) are infections that can be transferred from one person to another through any type of sexual contact. STDs are sometimes referred to as sexually transmitted infections (STIs) since they involve the transmission of a disease-causing organism from one person to another during sexual activity. It is important to realize that sexual contact includes more than just sexual intercourse (vaginal and anal). Sexual contact includes kissing, oral-genital contact, and the use of sexual "toys," such as vibrators. STDs probably have been around for thousands of years, but the most dangerous of these conditions, the acquired immunodeficiency syndrome (AIDS), has only been recognized since 1984.

Many STDs are treatable, but effective cures are lacking for others, such as HIV, HPV, and hepatitis B and C. Even gonorrhea, once easily cured, has become resistant to many of the older traditional antibiotics. Many STDs can be present in, and spread by, people who do not have any symptoms of the condition and have not yet been diagnosed with an STD. Therefore, public awareness and education about these infections and the methods of preventing them is important.

There really is no such thing as "safe" sex. The only truly effective way to prevent STDs is abstinence. Sex in the context of a monogamous relationship wherein neither party is infected with a STD also is considered "safe." Most people think that kissing is a safe activity. Unfortunately, syphilis, herpes, and other infections can be contracted through this relatively simple and apparently harmless act. All other forms of sexual contact carry some risk. Condoms are commonly thought to protect against STDs. Condoms are useful in decreasing the spread of certain infections, such as chlamydia and gonorrhea; however, they do not fully protect against other infections such as genital herpes, genital warts, syphilis, and AIDS. Prevention of the spread of STDs is dependent upon the counseling of at-risk individuals and the early diagnosis and treatment of infections.