This paper reviews the neurobehavioral and developmental effects of fetal drug exposure. The drugs most commonly associated with adverse developmental outcome include alcohol, anticonvulsants (particularly phenytoin and trimethadione), narcotics, and some environmental toxins. Major limitations of studies examining the consequences of prenatal drug exposure on development include inadequate control of other confounding factors, uncertain accuracy of drug histories, and outcome criteria that provide insufficient delineation of subtle developmental delays.