From May 1989 to February 1990, 1164 patients were followed in the Service of Orthopaedic Surgery and Traumatology at the CHUV, for the development of nosocomial infections (N.I.), in particular postoperative wound infections. Among them, 439 patients were treated conservatively and 725 underwent 833 operations. The global incidence of N.I. was 7.7/100 admissions. Urinary tract infections represented 57% of all N.I., postoperative wound infections represented 21% (with 12% superficial and 9% deep infections), pneumonias represented 20% (5 deaths), bacteriemias represented 2% (1 death) of the cases. The rate of infections was 1.1% for clean surgical interventions (n = 549), 0% for clean-contaminated operations (n = 87), 7.5% for contaminated operations (n = 40), 22.8% for dirty operations and 1.6% for unclassified operations (n = 122). Among the 19 postoperative wound infections, 6 were diagnosed after the patients were discharged. In conclusion, postoperative wound infections constituted only 20% of all N.I. observed in the Service of Orthopaedic Surgery and Traumatology and the rates of infection according to the types of interventions were low. On the other hand, 80% of the N.I. were observed at sites other then the wounds and were associated with a 0.5% mortality rate.