Cutaneous responses to tuberculin and control antigens were measured in 24 HLA-B7 and 39 non-B7 patients before and 5-44 (average 10.5) weeks after BCG immunotherapy for malignant melanoma. Delayed tuberculin hypersensitivity increased after immunotherapy (p less than or equal 0.0001). The averaged area of induration (48 h) detected in HLA-B7 patients was half the area of induration of non-B7 patients before (p less than or equal to 0.0184) and after (p less than or equal to 0.0007) BCG treatment. Cutaneous anaphylactic hypersensitivity (0.25 h) responses to 19 of 22 antigens were significantly smaller (p less than 0.05) in HLA-B7 patients after BCG immunotherapy (p less than or equal to 0.0001). HLA-B7 patients had specific delayed cutaneous hyporesponsiveness to tuberculin and nonspecific cutaneous anaphylactic hyporesponsiveness after BCG immunotherapy.