In this study, we analysed 13 samples of the French population--4147 non-related individuals living in Bordeaux, Brest, Caen, Dijon, Limoges, Lyon, Marseille, Nancy, Paris, Poitiers, Rennes, Strasbourg and Toulouse--all of whom were typed for 10 alleles of the HLA-A locus and 16 alleles of the HLA-B locus. The results showed a strong heterogeneity (chi 2 = 675.13 for 324 df, p less than 10(5)). A diagram has been drawn up, showing the matrix of genetic distances obtained thanks to the B2 of Balkrishnan & Sanghvi (1968). This diagram enables us to envisage the hypothesis of 6 homogeneous clusters. A partition of chi 2 was used to test this 6 luster hypothesis: Paris and Caen (p = 0.98); Nancy, Strasbourg (p less than 5%); Rennes, Brest (p less than 1%); Dijon, Lyon, Marseille (p = 0.89); Limoges, Poitiers (p = 0.18); Toulouse, Bordeaux (p less than 10(-5)). The heterogeneity within these clusters represents only 1/43 of the total heterogeneity.