To study teratogenicity of cocaine in humans, we studied three groups of pregnant women and their offspring: group 1, 50 women who abused cocaine only; group 2, 110 women who were polydrug abusers; and group 3, 340 who were drug free. All three groups were similar for socioeconomic status, cigarette smoking, and ethnicity. Maternal age of group 1 was similar to that of group 3, but group 2 mothers were significantly older. Gravidity was significantly higher in groups 1 and 2 compared with group 3. No statistical difference was found in spontaneous abortion rate among the three groups, but the stillbirth rate was significantly higher in group 1 (chi 2 = 6.89, P less than or equal to 0.01). All stillbirths were related to abruptio placentae. Birth weight, length, and head circumference were significantly decreased in infants in groups 1 and 2 compared with group 3 (P less than or equal to 0.0001), but no statistical difference was found between groups 1 and 2. The congenital malformation rate was significantly higher in group 1 compared with group 3 (chi 2 = 7.07, P less than or equal to 0.01). We conclude that cocaine abuse in humans significantly reduces weight of the fetus, increases the stillbirth rate related to abruptio placentae, and is associated with a higher malformation rate.