PIP: Epididymitis in the male and salpingitis in the female may cause permanent functional damage to the reproductive tract, resulting in infertility. Agents with proven connection to post-infection infertility are Neisseria gonorrhoeae and Chlamydia trachomatis. In men, infertility after chlamydia-associated epididymitis is uncommon, whereas in women sequelae after salpingitis--including chlamydia-associated disease--are the most common cause of acquired infertility. In a prospectively followed cohort of women who all sought pregnancy after one episode of laparoscopically verified acute salpingitis, 79/1025 (7.8%) were infertile because of post-salpingitic tubal occlusion, compared with 4/448 control women (0.9%). Important factors in post-salpingitic infertility were: number of episodes [relative risk (RR) after none, 1, 2, and 3 or more episodes were 1.0, 5.2, 11.3, and 19.8, respectively, amounting to a total infertility rate after salpingitis of 15%]; in women with only one episode, the severity of infection (mild, moderate, and severe; RR, 1.0, 1.8, and 5.6, respectively) and delayed care (less than 3 days and 3 or more days; RR, 1.0 and 3.0, respectively); use of contraceptives (non-contraceptors, pill users, IUD users, and 'other'; RR, 1.0, 0.3, 0.5, and 0.8, respectively); and non-chlamydial and chlamydial infection (RR, 1.0 and 1.7, respectively). Observations in infertile women suggest that an equally large number of women may have post-infectious tubal infertility also after asymptomatic salpingitis; in the majority of cases with serologic evidence of a passed genital chlamydial infection. Recently, a hypothesis has been presented that antigen-antibody reactions to chlamydial heat-shock proteins might be an important factor for the morphological tissue damage and scarring leading to impaired fertility. Post-pelvic inflammatory disease associated with sexually transmitted disease infertility is acquired and, hence, preventable.