Higher susceptibility of newborns to infections has been attributed to the hypo-responsiveness of their cellular immune system. Here we compared the activation status and expression of cytokines and cytotoxic molecules of cord versus maternal peripheral blood mononuclear cells in an African population. Human leucocyte antigen-DR was expressed on a lower percentage of cord compared to maternal gammadelta and CD3(+) T cells. Similarly, a lower proportion of cord versus maternal gammadelta and CD3(+) T cells displayed perforin, granzyme B and cytokine activity either ex vivo or following non-specific stimulation in vitro. In contrast, comparable proportions of cord and maternal CD94(+) CD3(-) natural killer (NK) cells showed perforin and granzyme B expression ex vivo. We conclude that cord blood gammadelta and CD3(+) T cells are functionally hypo-responsive as reflected by reduced numbers of such cells expressing either an activation marker, T helper 1 (Th1) and Th2 cytokines or cytotoxic effector molecules. The similarity in numbers of cord and maternal CD94(+) CD3(-) cells expressing cytotoxic effector molecules suggests that neonatal Africans' NK cells may be functionally mature.