To determine the microbiological causes of pelvic inflammatory disease, 43 women with acute salpingitis (AS) and 160 controls were studied. Amongst AS women there were significantly higher endocervical isolation rates of Neisseria gonorrhoeae (54% vs 6%), Chlamydia trachomatis (40% vs 13%), Mycoplasma hominis (60% vs 19%), enterobacteria (26% vs 11%) and anaerobic bacteria (58% vs 29%). A polymicrobial pathogenic endocervical flora was present in both gonococcal and non-gonococcal AS. Laparoscopic sampling of the fallopian tubes rarely provided useful microbiological data but did reveal the inaccuracy of clinical diagnosis of AS. Thirty-four male consorts of AS women were investigated; 20 had gonorrhoea and 27 had non-gonococcal urethritis (NGU). A high proportion of infected men had asymptomatic gonorrhoea (35%) and/or asymptomatic NGU (56%). These findings had implications for the management of AS.