The neurological status of 9- and 30-day-old infants, as assessed by the Prechtl neurological examination, was significantly and differentially related to prenatal exposure of cigarettes, marijuana, and alcohol. Data on approximately 250 babies, born to healthy, white, predominantly middle-class women, were analyzed using discriminant function analyses controlling for potentially confounding variables. Prenatal cigarette exposure was associated with hypertonicity and increased nervous system excitation, particularly at 30 days, prenatal marijuana exposure was associated with symptoms similar to mild narcotic withdrawal, and prenatal exposure to relatively low levels of alcohol was associated with slightly lowered nervous system arousal at 9 days of age. The results were related to behavioral observations on neonates exposed to drugs prenatally.