Crude merozoite antigens from P. falciparum were used to analyse the proliferative response of peripheral blood mononuclear cells from 114 inhabitants of the village of Dielmo (Senegal, West Africa), who are exposed continuously to malaria transmission. The high or low responses to merozoite antigens obtained in lymphocyte stimulation assays were correlated to the presence or absence of parasites, to the IFN-gamma production and to the HLA-phenotype. High responders produced high levels of IFN-gamma while low responders did not secrete IFN-gamma (23/27). The two HLA phenotypes HLA-B51 and HLA-DR1 were significantly associated with high response (p < 0.05).