In this multicentre study, 883 evaluable patients undergoing orthopedic surgery were randomly assigned to receive antiinfective prophylaxis with either ceftriaxone (Roce-phin®) or cefamandole. 25 patients in the ceftriaxone group and 29 patients in the cefamandole group (5.6 vs 6.5%) presented with infectious complications within the first 60 days after surgery. Delayed deep wound infections developed in only 1 of 435 patients in the ceftriaxone group compared with 4 of 413 patients in the cefamandole group. Both drugs were well tolerated. The infection rate was twice as high after surgery in conventional operating theatres than after treatment in hypersterile operating theatres (3.3 vs 6.5%); this difference is not statistically significant