The prevalence and patterns of gonococcal and chlamydial infection were investigated in a prospective microbiological study on 3,395 women requesting abortion and the sexual partners of culture positive women (organism identified). Neisseria gonorrhoeae was found in only 1.8% of 3,395 women during the whole study period of 7 years, but Chlamydia trachomatis in 13.5% of 1,635 women in the last 3 years. Women with positive cultures were significantly younger (p less than 0.001), and more frequently single (p less than 0.001) than those with negative cultures. Single women had more partners (mean 1.5) than those in an established relationship (mean 1.1). Almost all women with gonorrhea were single. Of the males, 62.7% were examined, of whom 47.3% had positive cultures. Twenty per cent of culture positive males had gonorrhea. A high prevalence of positive cultures in the males was only found where chlamydial cultures had been positive in the female. All women and men with positive culture results received antibiotic treatment before or after the abortion procedure. The incidence of laparoscopically verified post-abortion salpingitis was low, at 0.57%, while a clinical diagnosis of endometritis was made in 3.3%. Routine pre-operative microbial screening for Chlamydiae trachomatis should be considered for all women requesting abortion. Tracing and screening for chlamydial and gonorrheal infection of sexual partners of culture-positive women is necessary as a preventive measure.