This report is based on a previously described sample of 291 mothers-to-be and on an additional 129 subjects. Among these 420 predominantly middle class pregnant women, approximately 3 percent used marihuana regularly during pregnancy. For assessing the effect of marihuana on pregnancy variables and the offspring, the mothers-to-be were matched in terms of nicotine and alcohol use. Marihuana use was associated with a shorter gestation period and a decreased maternal weight gain. No effect on birth weight, length of labor or difficulty in birth were observed. Consistent with the earlier report, babies born to women who smoked more than five joints per week during pregnancy demonstrated marked tremors and startles and altered visual responsiveness at 2-4 days of age. These symptoms had attenuated by 30 days and no developmental impairments were observed in any of seven babies who had reached one year of age born to women who had smoked 2 joints or more per week during pregnancy.