Thirty-six evaluable patients with advanced breast cancer who had failed prior CMF therapy [15 (42%) as adjuvant treatment and 21 (58%) for advanced disease] were treated with a combination of vincristine, doxorubicin, and mitomycin (VAM). There was one CR and 10 PR, giving a response rate of 31% (P, 95% confidence interval, 15%-47%). Response was not significantly related to age, performance status, disease-free interval, dominant site of disease, number of sites of disease, or estrogen receptor status. The median duration of response was 5 months for patients attaining CR or PR and 4.6 months for patients with stable disease. The median survival for patients with CR or PR of 7.9 months was not better than for those with stable disease (8.0 months), but both groups had significantly longer survival than those with initial progression. Patients who received VAM after failing adjuvant CMF had a 53% response rate (8 of 15), as against a 14% response rate (3 of 21) in those failing CMF for advanced disease (P less than 0.05). In spite of this difference, the survival distributions for these two groups were not significantly different. Myelosuppression was moderate and no cardiac toxicity was seen. The addition of mitomycin to vincristine and doxorubicin in previously treated patients does not appear to improve the results obtained with vincristine and doxorubicin alone.