The HLA A*2, Bw*50-BF*S07-C4 A*2, B*1 linkage group was transmitted unambiguously in four unrelated Tunisian families. In one of these, another allele association, also carrying BF*S07, HLA A*9, Bw*50-BF*S07-C4 A*1, B*1, was encountered. The previously reported linkage disequilibrium between BF*S07 and HLA Bw*50, a subtypic specificity of HLA Bw*21, is confirmed in our study. The C4 A*2, B*1 haplotype, rare in the other populations until now studied, seems more frequent in Tunisia since it has been also found linked to HLA A*11, B*27 and BF*S in one of these families. Other allele associations were unambiguously demonstrated with predominantly the C4 A*3, B*1 haplotype, particularly a rare HLA A*3, B*18-BF*F1-C4 A*3, B*1 linkage group. A silent gene at the C4 A locus was found linked to HLA B*8.