The bacteriology of acute pelvic inflammatory disease (PID) was studied in 65 women. Endometrial, endocervical and vaginal cuff cultures were taken. In some cases blood cultures and cultures from the cul-de-sac or pelvic abscess were also obtained. Mixed organisms (aerobes and anaerobes) were the most common isolates from the endometrial, endocervical or vaginal cuff cultures, present in 40%. Neiseriagonorrhoeae was isolated in 8 (12.30%) endocervical specimens. Anaerobes were the most common bacteria recovered from cul-de-sac aspirates, pelvic abscesses and blood cultures. The combination of gentamicin, penicillin and metronidazole was the most common antibiotic scheme used. However, other antibiotics as cefoxitin and clindamycin were also used according to the sensitivity test. These data support the polymicrobial etiology of the disease and suggest: (1) the high incidence of anaerobic or mixed infections, and (2) the relatively low incidence of gonococcus in the studied cases.