One hundred and fourteen evaluable patients with metastatic breast cancer were treated with a program consisting of 5-FU, Adriamycin, cyclophosphamide (FAC) and nonspecific immunotherapy with Levamisole. The results of this treatment program were compared to those observed with FAC and Bacillus Calmette Guerin (BCG) and FAC chemotherapy alone, both groups treated prior to the study reported in this paper. The overall response rates and complete response rates for all three treatment regimens were identical. The duration of remission, survival of all patients and survival of responders was similar for both chemoimmunotherapy regimens, being superior to the FAC chemotherapy alone group. Immunotherapy with Levamisole was well tolerated and side-effects were experienced by less than one-fourth of the patients. Overall, Levamisole was better tolerated than BCG and was easier to administer than the latter drug. These results suggest than nonspecific immunotherapy with Levamisole might prolong remission and survival of patients with metastatic breast cancer. Since the results achieved with BCG and Levamisole appear similar, the therapeutic ratio favors the use of Levamisole.