Several studies published during the last fifteen years seem to demonstrate that major risks, i.e. congenital malformations in the offspring and increased rate of spontaneous abortions, are associated with occupational exposure to anesthetic gases (halothane and nitrous oxide) in operating rooms. In view of the severity of the potential risk, we have: 1) analyzed risk factors in the light of epidermiologic and experimental studies; 2) determined the threshold levels of air pollution for these risk factors; 3) analyzed the situation in the Grenoble Hospital and the means of dealing with it.