Objective: The primary purpose of this study is to investigate the impact of prenatal cocaine exposure, while controlling for other factors that influence infant outcome. Method: These preliminary data are from an ongoing prospective study of prenatal cocaine and/or crack exposure. Detailed information is collected about the use of cocaine, crack, alcohol, tobacco, marijuana, and other drugs during each trimester of pregnancy. Results: Women who use cocaine and/or crack during pregnancy differ from those who do not. The women who use cocaine are older, more likely to be black, and less likely to be married. They also use more tobacco, alcohol, and marijuana during pregnancy than do nonusers of cocaine. When these differences between the exposure groups are controlled, preliminary analyses indicate there is no significant effect of prenatal cocaine use on infant growth and morphology. Conclusions: Future research needs to address the effects of prenatal cocaine and/or crack exposure on central nervous system development and on the long-term development of exposed offspring.