The SWOG carried out a Phase II evaluation of rubidazone in patients with advanced breast cancer. Good risk patients were given rubidazone 150 mg/m2 IV every three weeks. Poor risk patients were given a 25% dose reduction at the start of treatment. Rubidazone dose was increased or decreased depending on toxicity. One patient went into complete remission, four had partial remission and nine had stable disease. Forty-two patients showed increased disease on treatment. No cardiotoxicity was seen, but other common toxicities noted included mostly mild to moderate myelosuppression, nausea, vomiting and alopecia. This study failed to indicate significant antitumor activity of rubidazone in patients with advanced breast carcinoma.