Thirty one patients with gallbladder cancer (GBC) and 32 healthy controls were typed using antisera against 12 HLA-A, 31 HLA-B, 7 HLA-C and 13 HLA-DR antigens. The DR4 frequency of 61.3% (19/31) in GBC was significantly different from that of 28.1% (9/32) in the control (p = 0.00794 by Fisher's exact test). The relative risk and the etiologic fraction were 4.0 and 0.46, respectively.