The HLA-A, -B, -DR and DQ phenotypes have been defined in a panel of 217 Lebanese. These subjects were all unrelated, belonged to different religious communities and originated from the various provinces of Lebanon. All the broad class I specificities tested, except splits A25(10), B54(22) and B56(22), were present in this panel. When HLA-A and -B antigen frequencies were compared with data on the Caucasoids, Negroids and Orientals, several similarities in antigen frequencies could be found between some frequencies observed in the Lebanese and those observed in the Negroids and/or Orientals. There were no frequencies equivalent to those particular to the Caucasoids. In addition, two groups of class I antigens could be distinguished: a first group (A32, B14, B18, B35, B38, B39, B41 and B50) showing higher frequencies, and a second group (A31, B27, B60 and B62) showing lower frequencies than those observed in the Caucasoids, Negroids and Orientals. However, when analysed separately, several mediterranean ethnic groups, notably the Greeks and Italians, have a frequency profile equivalent to that of the Lebanese, with the exception of the B41 specificity, which is particularly high in the Lebanese (14.2%). The data concerning the class II antigens are the most interesting. All the specificities were present in the panel. The HLA-DR5 is the highest frequency of DR antigens in the present panel (58.9%) and nearly all DR5 positive individuals are DR11. The DR11 allele accounts for 33.1% of the total DR gene frequency. The highest DQ antigen frequency is that of DQ3 (76.4%), the majority of which is DQ7 (66.4%). We observed a high DR11-DQ7 haplotype frequency (29.4%) with a significant delta value for linkage disequilibrium. There is no linkage disequilibrium between B41 and DR11. The commonly observed linkage disequilibrium between the DQ5 allele, and the DR1, DR2, DR10 and DR14 alleles are not significant in this Lebanese panel.