CD1 molecules are able to present unusual antigens, lipids or glycolipids from mycobacterium cell walls to T lymphocytes. Previous studies have suggested that polymorphism of these genes is very limited, in contrast with classical major histocompatibility complex (MHC) antigen-presenting molecules. Our aim was to study possible allelic variations of exons 2 and 3, encoding for the alpha1 and alpha2 domains, respectively, of human CD1A, -B, -C and -D genes. We analyzed genomic samples of unrelated, healthy individuals from different ethnic background: 70 Caucasians from Europe, 33 Black Africans (13 from Tanzania and 20 Zulus), 19 Caucasians from the Sahara and 44 Asian individuals. We have found CD1A to be a biallelic locus with a common allele which was present in the majority of the individuals studied. The second allele differed from the common one by a single-point mutation, resulting in a change of Cys to Trp at position 52 in the alpha1 domain. This second allele was found in heterozygosis in 7 out of 70 Caucasians from Europe (allelic frequencies P=0.95 and q=0.05). In the Chinese population, we found the second allele present in heterozygosis in 19 from the 44 individuals studied, and we also found 6 homozygous individuals for the second allele (allelic frequencies P=0.64 and q=0.35). In addition, we detected a synonymous mutation (C to T transition) in codon 34 of CD1C exon 2 in 4 out of 20 Zulus and in 2 of the 13 Blacks from Tanzania.