In a randomised study, comprising 166 patients, aged 25–75 years, the effect of a single preoperative dose of Clindamycin was compared with no antibiotic treatment at all in patients undergoing elective abdominal hysterectomywith drainage of the upper part of the vagina. Febrile Morbidity, frequency of postoperative infections, the amount of secretion and the number of hospital days were recorded. Preoperative administration of clindamycin resulted in a reduction (from 24% to 14%) in the febrile morbidity, and in the amount of secretion (from 24 to 12.5 ml) both of marginal statistical significance, whereas the reduction in the frequency of postoperative infections (from 19 to 10%) was without statistical significance. A statistically significant reduction in the hospitalisation period (from 8.4 to 7.9 days) was observed. The frequency of urinary tract infections was similar in the two groups. No adverse reactions occurred in connection with the clindamycin treatment.