Sexually transmitted diseases (STDs) have shown a considerable resurgence in recent years both in number of cases and in spread of new infectious agents. The spread of STDs is favored by numerous factors including the liberalization of sexual behavior made possible by reliable contraception. Information on STDs has not been widely diffused. Changes in the status of women and the development of means of communication and transportation have encouraged less rigid control of sexual behavior. STDs themselves have often escaped diagnosis or not been cured despite treatment, increasing the risk of spread. Numerous organisms cause STDs, from external parasites to life-threatening viruses. 60% of upper genital tract infections that can lead to sterility, tubal alterations, ectopic pregnancy and pain result from STDs. Chlamydia infections are insidious and chronic, and cause greater damage with each recurrence. The risk of STDs should be considered in contraceptive choice along with other indications and contraindications. Combined oral contraceptives provide protection against acute upper genital tract infections. The protective role has been explained by scanty and highly viscous cervical mucus forming a barrier against germs and by reductions of menstrual flow, myometrial activity, and inflammation. It is actually uncertain whether combined oral contraceptives protect against latent chlamydia infections, since higher rates of cervicitis caused by chlamydia have been found in pill users. In situations carrying risk of STDs, pill users should be protected by a supplementary barrier method. IUDs have been implicated in numerous studies in acute pelvic infections. Possible explanations are the local trauma and inflammations due to the physical presence of the IUD, more abundant bleeding, absence of a cervical barrier to motile sperm that could be a vector for germs, and possible ascent of the infectious agent on the string. Other risk factors are involved. Epidemiologic studies indicate that the spermicides benzalkonium chloride and nonoxynol 9 have a protective effect against gonococcus, trichomonas, and chlamydia as well as cervical cancer. The protection is not absolute and is associated with the use of barrier methods. Condoms provide an excellent barrier against gonorrhea, chlamydia, cytomegalovirus, herpes, hepatitis B, and HIV infection. Use of spermicides may increase protection even more.