One hundred and sixty-four patients undergoing abdominal hysterectomy for benign diseases were prospectively evaluated. The efficacy and safety of surgical prophylaxis with a single dose of the long-acting cefonicid was compared to the standard three dose regimen of cefazolin. Prophylaxis was successful in 82 of 85 (96.5%) patients receiving cefonicid and in 77 of 79 (97.5%) patients receiving cefazolin. No serious adverse effects were encountered with both drugs. It is concluded that single dose intravenous cefonicid, when given pre-operatively, is as safe and effective as the standard multiple dose regimen of cefazolin in patients undergoing elective abdominal hysterectomy.