A variety of evidence suggests that chronic exposure to low doses of anesthetic gases, as occurs in the occupational setting, is a risk factor for spontaneous abortion and congenital defects. The major epidemiologic studies are reviewed, and it is suggested that, due to significant flaws in the design and conduct of these observational studies, there is inadequate evidence to conclude that occupational exposure to anesthetic agents causes increased rates of spontaneous abortion or congenital anomalies.