The frequency of human leukocyte anti- gen DRB1 alleles was determined in a cohort of 194 Kuwaiti Arabs consisting of 80 schizophrenia patients and 114 ethnically matched healthy controls, using a polymerase chain reaction-sequence specific primers method. A total of 12 DRB1 alleles were identified in this Kuwaiti cohort. A statistically significant difference was detected in the frequency of alleles DRB1(*)04 and DRB1(*)13 between the schizophrenia patients and controls. Allele frequency of DRB1(*)04 in schizophrenia patients was 14% compared with nearly 7% in controls (P = 0.028). For DRB1(*)13, the allele frequency was found to be 18% in schizophrenia patients compared with 9% in the controls (P = 0.015). For alleles, DRB1(*)03, DRB1(*)07, and DRB1(*)16 the frequency was higher in controls compared with schizophrenia patients. The frequency of DRB1(*)01, DRB1(*)08, DRB1(*)10, DRB1(*)11, and DRB1(*)15 alleles was almost identical in schizophrenia patients and controls. For the remaining alleles, the differences between the two groups were not statistically significant.