The behavior of third-generation Israeli neonates belonging to two ethnic groups--Ashkenazic infants (n = 20) and Sephardic infants (n = 20)--and the behavior of a group of full-term Panamanian infants (n = 30) were compared in order to examine cross-cultural and interethnic predispositions. The Israeli and Panamanian infants differed on 5 of a total of 27 neonatal behavioral assessment items: the difference in 3 of these items, representing the autonomic stability and motor clusters, exceeded 1 scale score. A comparison of the two Israeli ethnic subgroups with the Panamanian group (Duncan's multiple-range test) revealed significant differences between Ashkenazic and Sephardic infants on 2 auditory habituation items, whereas the Panamanian infants differed significantly from both Israeli subgroups on 10 of the items, representing the motor, range of state, and autonomic stability clusters. These results corroborate previous observations concerning cross-cultural neonatal behavioral differences and the possible role of environmental factors in the ongoing modeling process of human behavioral traits and personality.