The efficacy of a three-dose, perioperative regimen of cefazolin or placebo in reducing postoperative infectious morbidity was evaluated in a double-blind study in 206 patients undergoing elective vaginal or abdominal hysterectomy. Postoperative infectious morbidity was defined as: an oral temperature of 100.4 F (38 C) or greater on any two postoperative days (excluding the first day), positive bacteriologic cultures, or pus from a wound. In premenopausal patients, cefazolin significantly reduced the incidence of postoperative infectious morbidity; 19% of the cefazolin group who had abdominal hysterectomy had evidence of infection compared to 71% of the placebo group, and 10% of the cefazolin group who had vaginal hysterectomies had evidence of infection compared to 37% of the placebo group. In postmenopausal patients undergoing abdominal hysterectomy, cefazolin also reduced the incidence of postoperative infection compared to placebo, but the difference was not significant (20% compared to 37%).