PIP: Directed to the health care professional, this review covers the current concepts of pelvic inflammatory disease (PID) affecting adolescent and young adult women. It defines PID and discusses the magnitude of the problem, risk factors (sexual activity, age, method of contraception, history of previous PID, history of gonococcal of chlamydial lower genital tract infection, and uterine instrumentation), etiologic agents (N. gonorrhea, aerobic and anaerobic bacteria, chlamydia trachomatis, genital mycoplasmas, and other pathogens), pathogenesis, clinical and laboratory features, diagnostic evaluation, differential diagnosis, treatment, and sequelae. The Centers for Disease Control define acute PID as "the acute clinical syndrome (unrelated to pregnancy or surgery) attributed to the ascent of microorganisms from the vagina and endocervix to the endometrium, fallopian tubes, and/or contiguous structures." The true incidence and prevalence of PID in women is uncertain. Recent data show an increase to 267,200 in the average annual number of hospitalizations for PID during the 1975-81 period for women 15-44 years of age. PID occurs rarely in sexually inactive women. The large number of PID cases among adolescents reflects in part the high proportion of sexually active females in that group. The risk of developing PID in sexually active females is inversely related to age; 1/3 of all patients in Westrom's series were 19 years of age or younger at the time of their 1st PID episode, and 69% of all women with PID were younger than 25 years. Women who have had 1 episode of PID have a 20-25% chance of developing subsequent episodes. A large series of PID cases verified by laparoscopy has shown that only a small proportion of patients (3%) present with a severe clinical illness. Low abdominal pain is the most common symptom and may be present for variable periods of time prior to diagnosis. Other common symptoms include vaginal discharge (55%), irregular vaginal bleeding (36%), urinary symptoms (19%), nausea and vomiting (10%), and proctitis symptoms (7%). The major goals of therapy in PID are to prevent infertility and other long-term sequelae. About 15% of patients fail to respond to initial antibiotic therapy, 20% experience recurrences, 20% develop involuntary infertility, and 8% of post-PID patients who conceive have an ectopic pregnancy. Early diagnosis and treatment reduces the risk of residual tubal damage.