Cellular responses to synthetic peptides from the Liver Stage Antigen-1 (LSA-1) from Plasmodium falciparum were determined in 229 Gabonese children. HLA class I and II typing (by PCR-SSP and-RFLP, respectively) revealed that HLA-A* 19,-B* 17 (and-B* 70),-DRB1* 05,-DQA1* 0102,-DQB1* 0602 and-DPB1* 0402 were the most frequent types or alleles at each locus. The DQB1* 0201 and DQB1* 0301 alleles were present at a higher frequency among IL-6 and IFN-γ responders to the LSA-Rep and LSA-CTL peptides, respectively, and a higher proportion of these responders carriedA* 19 or B* 53. The DRB1* 06 type was positively related to the IL-10 production in response to the LSA-CTL peptide, and responders presented mainly A* 2. The specificity A* 10 was negatively associated with the cellular response to the LSA-J peptide. These results suggest a degree of genetic regulation of specific immune responses by HLA-A, operating at the pre-erythrocytic stage of development of P. falciparum in this Central African population.