The performances of three groups of neonates on the Brazelton Neonatal Behavioral Assessment Scale were compared to determine if cultural differences exist. Subjects were 90 full term, healthy infants; 30 born in Puerto Rico, 30 black and 30 white born in Florida who were administered the scale within the first two days of life. Eight summary variables based on the four a priori dimensions of interactive processes, motoric processes, state organization, and physiological organization were selected. For each summary variable a mean score was calculated after having recoded the items comprising each cluster on the same direction. The three groups of neonates were compared by computing a one way analysis of variance for each variable. Results showed main effects for six of the summary variables indicating the existence of cultural differences between Puerto Rican and black and white North American newborns. Puerto Rican babies had better orienting and following, were easier to console, and more capable of controlling their physiological response to stress. Results are discussed in terms of cultural expectations, mother/infant interaction, and infant adaptation to environment. (SB)