A revised Prechtl Neurological Examination was administered to 510 singleton infants at term conceptional age to assess the influence of gestational age, race, and sex on neurobehavioral responses in a "typical" newborn population. The infants were born at 1 of 5 centers and were subjects of the NIH Collaborative Study on Antenatal Steroid Therapy. Of these babies, 392 were born at less than 37 weeks gestational age, whereas 118 infants were born at greater than or equal to 37 weeks. Of a total of 50 items of interest, 12 differed significantly based on race, 14 items differed in terms of gestational age at birth, and 5 items were influenced by the sex of the baby. These data suggest that singleton preterm infants born at differing gestational ages should not be considered to comprise a homogeneous sample. Further, caution should be exercised when considering babies of heterogeneous race groupings, and the babies' sex has minimal impact on neurobehavioral responses at term conceptional age.