In the present study we have investigated the HLA-SB antigen distribution in 65 unrelated Israeli Ashkenazim and non-Ashkenazim and in a panel of 18 local homozygous typing cells (HTC). Two locally derived SB reagents, anti-SB2 and SB3, were also studied. The HLA-SB allele frequencies in the Israeli sample ranged from 0.02 for SB1 to 0.47 for SB4 while SB5 was absent. SB3 had a higher frequency in non-Ashkenazim (0.11) as compared to Ashkenazim (0.06) but this difference was not significant. On the whole, the allele frequencies for the 5 HLA-SB antigens studied were in the range observed in non-Jewish Caucasoid populations with some minor variations. Two of eighteen local HTC's were found heterozygous for SB, demonstrating that homozygosity for HLA-A, B, C, D and DR does not indicate homozygosity for HLA-SB. The local anti-SB2 and SB3 typing reagents gave concordant results when compared with the NIH reference typing cells in population studies.