Dual association of HLA DR2 and DR3 with primary sclerosing cholangitis. Human leukocyte antigen typing was performed in 81 patients with primary sclerosing cholangitis to investigate reported associations between human leukocyte antigen type and this disease. The results showed a significant increase in the frequency of the antigens B8 and DR3 compared with controls (53% vs. 23%, p less than 0.0005, and 56% vs. 21%, p less than 0.0005). This was caused by a significant rise in the frequency of the human leukocyte antigen A1 B8 DR3 haplotype (32 of 81 patients, 40% vs. 12 of 100 patients, 12%, p less than 0.0005). By contrast, a significant reduction was seen in the frequency of the antigens B44 and DR4 (12% vs. 31%, p less than 0.005, and 12% vs. 34%, p less than 0.001, pc less than 0.011) because of the complete absence of the B44 DR4 haplotype in the patient group (p = 0.027, Fisher's exact test). When all the DR3-positive individuals (including the DR2/DR3 heterozygotes) were eliminated, a significant secondary association with DR2 was noted, 25 (69%) of 36 remaining patients being DR2-positive compared with 27 (34%) of 79 DR3 negative controls (p less than 0.0005, pc less than 0.006). Only 9% of the patients were DR2-positive and DR3-positive. Kaplan-Meier analysis demonstrated that survival was not influenced by the presence of either haplotype nor by the individual antigens. Patients who were DR3-positive were first seen at a significantly younger age than those who were DR2-positive (mean ages = 33 yr and 44 yr, respectively, p less than 0.002, Student's t test). 