A study was performed of 102 obstetric-gynecologic patients who were thought to have sepsis or a pelvic abscess. Fifty-three of these women received chloramphenicol and 49 received clindamycin. In addition, all patients received penicillin or a similar antibiotic and an aminoglycoside. Similar clinical results were observed with the two treatment regimens. In eight of the 49 patients who received clindamycin and in three of 52 patients who received chloramphenicol, use of the drug was discontinued because of side effects. These combinations of antibiotics did not eliminate the necessity for major operative drainage, which was required in 40 patients. Resistant organisms were recovered from only two patients. Although sepsis and shock were most frequently associated with gram-negative aerobic bacteremia, they occurred in two patients in whom only anaerobes were recovered from blood cultures. Because the clinical results with the two regimens were equivalent, a decision to use either clindamycin or chloramphenicol should be based on the individual physician's assessment of the toxicity of these agents.