Two hundred patients with metastatic breast cancer who were treated with combination chemotherapy and nonspecific immunotherapy with BCG or MER were skin tested prior to, and at regular intervals during the administration of chemotherapy with a battery of six antigens (Dermatophytin, Varidase, candida, mumps, PPD, and KLH). Delayed-type hypersensitivity responses to this battery of antigens were analyzed to assess whether they correlated with ability to respond to chemotherapy, length of survival, and a number of other host and tumor characteristics of known prognostic significance. Responsiveness to individual recall antigens or the number of positive skin test responses did not correlate with overall or complete response rates. The correlation did exist with KLH, a primary antigen. A positive response to two or more antigens correlated with a longer survival. Inability to mount a skin test response to any antigen correlated with poor survival. PPD conversions during serial BCG administration did not correlate with a better prognosis. Serial skin testing with a battery of antigens did not correlate with prognosis. Skin test responsiveness to the antigens used in this study did not correlate with the other pretreatment factors of prognostic importance such as tumor burden, absolute lymphocyte count, performance status, prior radiation therapy, menopausal status, and age. Therefore, responsiveness to skin testing with these antigens appears to be an independent prognostic variable and should be incorporated in the planning and analysis of systemic treatment programs in metastatic breast cancer.