The HLA-A, -B, -C and DR loci antigen frequencies were determined, respectively, on 1145, 558 and 352 healthy nonrelated Saudi family members. B21, CW4, CW7, and Dr7 showed the highest gene frequencies, of 14.6%, 28.3%, 7.4% and 19.5%, when compared to other populations. Haplotypes A2-B5, A32-B51, A26-B8, A2-B21, A28-B35, Aw19-B21 and B21-CW4 showed the highest frequencies when compared to other populations. Gene frequencies of 14.6% and 20.2% for B21 and Aw19 antigens, respectively, are highest among Middle East populations. Gene frequencies for A1 (10.5%), A2 (24.9%), A3 (8.9%), A9 (16.7%) and A28 (7.9%) are similar to the 10.1%, 24.9%, 8.3%, 16.8% and 7.7%, respectively, reported for the Turkish population. Also, gene frequencies for B5 (18.5%), B21 (14.6%) and B35 (10.2%) are very close to 17.1%, 14.0% and 10.2%, respectively, reported in the Yemenite population. The above results suggest some influence of other populations on the 'pure' Arab population.