Sixty-two patients with Crohn's disease and 51 with ulcerative colitis were HL-A typed. Phenotype frequencies were calculated and compared with those of a control group of 335 individuals. A higher frequency of HL-A17 was found among the Crohn's disease patient but this was not significant. However, HL-A17 has been included in two studies on Crohn's disease and the combined relative risk is 3.24 which significantly deviates from 1 unity. No statistically significant differences in the HL-A antigen distribution were found among the patients with ulcerative colitis.