We studied HLA class I (HLA-A, -B) and class II (HLA-DRB1, -DQB1) alleles by PCR-SSP based typing in 95 Mexicans from the state of Aguascalientes to obtain information regarding allelic and haplotypic frequencies and their linkage disequilibrium. We find that the most frequent haplotypes in the state of Aguascalientes include four Native American, three European and one Asian haplotypes. Admixture estimates revealed that the main genetic components in the state of Aguascalientes are Native American (54.53 ± 3.22% by ML; 44.21% of Native American haplotypes) and European (44.34 ± 0.45% by ML; 40.53% of European haplotypes), and a relatively low African genetic component (1.13 ± 2.33% by ML; 5.26% of African haplotypes).