Presented are blood culture results obtained from 200 patients with post-cesarean section endomyometritis treated with either penicillin-gentamicin or clindamycin-gentamicin. Their clinical course is correlated to their blood culture results by the fever index. Fifty-three percent of the 60 organisms isolated from 48 patients were anaerobic bacteria. Patients from whose blood cultures anaerobic bacteria were recovered had higher fever indexes than did those with aerobic isolates (P less than .05). Clindamycin-gentamicin patients from whose blood cultures anaerobic organisms were isolated had less febrile morbidity than did comparable penicillin-gentamicin patients. Patients with Bacteroides fragilis bacteremia had the highest fever indexes overall. Therefore, patients with post-cesarean section endomyometritis have less febrile morbidity if they are initially treated with a drug effective against anaerobic bacteria, especially B fragilis.