The effect of exposure to inorganic mercury on the pregnant woman and her foetus has received little attention. Transport of elemental inorganic mercury into foetal tissues has been reported, and prior studies indicate a higher incidence of adverse pregnancy outcome. The effects of occupational exposure to inorganic mercury on pregnancy were investigated among 46 exposed women workers: controls were 19 women working in non-production areas of the same factory. There were 104 recorded total pregnancies during the period 1948-77. The study revealed a higher frequency of adverse reproductive outcomes, especially congenital anomalies, among the women exposed to inorganic mercury levels at or substantially lower than 0.6 mg/m3; no significant differences in the stillbirth or miscarriage rates were noted between the two groups of women. The overall foetal death rate in this study was similar to New York state (USA) and national levels for the same period.