In order to study HLA haplotypes in congenital adrenal hyperplasia secondary to 21 hydroxylase (21-OH) deficiency, HLA typing was performed in Three families with six affected members. HLA genotypes revealed that in family number 1, two of the three affected members with CAH 21-OH presented salt-losing syndrome and were genotypically identical for HLA A1, B15/A32, Bw35. Family number 2 had two affected members with CAH 21-OH and salt-losing and they were genotypically identical for HLA A11, Bw51/A29, B12. In family number 3, only one of three members presented CAH 21-OH without salt-losing and was HLA homozygous A29, B12/A29, B12; the other two family members were heterozygous with genotype HLA A2, B37/A29, B12. The study suggests that haplotype HLA A29, B12 is related to CAH 21-OH with or without salt-losing syndrome.