To demonstrate genetic susceptibility to Creutzfeldt-Jakob disease (CJD), 10 Japanese patients with pathologically proved CJD and 6 patients with clinically definite CJD were tissue typed for 48 class I and 14 class II human leukocyte antigen (HLA) specificities. The patients were scattered throughout Japan and there were no consanguineous relationships. Among 62 HLA specificities, HLA-DRw53 and DQw3 were found in all pathologically proved CJD cases. When the frequencies of the HLA antigens in the 16 CJD cases were compared to those of normal Japanese, a highly significant (p less than 0.005) increase was found for HLA-DQw3 in the CJD group. The present findings provide evidence for genetic control of susceptibility to CJD in humans.