The non‐classical human leucocyte antigen (HLA) class I locus, HLA‐G, shows a low protein polymorphism and a more varied DNA (eight proteins and 28 alleles). HLA‐G DNA polymorphism accounts mainly for changes at third codon bases of the protein coding exons; this does not imply amino acid change in most cases. This relatively high HLA‐G DNA polymorphism in comparison with their protein polymorphism suggests that evolutionary forces are acting upon HLA‐G for invariance. This may be related to the immunotolerogenic function postulated for HLA‐G.