These guidelines for the treatment of patients who have sexually transmitted diseases (STDs) were developed by CDC staff members after consultation with a group of invited experts who met in Atlanta on February 10-12, 1997. The information in this report updates the "1993 Sexually Transmitted Diseases Treatment Guidelines" (MMWR 1993;42[no. RR-14]). Included are new recommendations for treatment of primary and recurrent genital herpes and management of pelvic inflammatory disease; a new patient-applied medication for treatment of genital warts; and a revised approach to the management of victims of sexual assault. Revised sections describe the evaluation of urethritis and the diagnostic evaluation of congenital syphilis. These guidelines also include expanded sections concerning STDs among infants, children, and pregnant women and the management of patients who have asymptomatic human immunodeficiency virus infection, genital warts, and genital herpes. Guidelines are provided for vaccine-preventable STDs, including recommendations for the use of hepatitis A and hepatitis B vaccines.