The goal of this clinical protocol is to use a novel chemotherapeutic agent, bryostatin-1, in the treatment of metastatic breast cancer. A secondary goal of this study is to examine the pharmacokinetics and biologic endpoints for this drug when administered either as a 24 or 72 hour infusion. Patients who have failed multiple other chemotherapeutic regimens are randomized to either of these two dose schedules. They are admitted to GCRC inpatient floor for the first dose of chemotherapy. During this admission the patient's blood is drawn for pharmacokinetics and other biologic studies. For subsequent doses the patient comes to the outpatient GCRC where they are hooked to a continuous infusion pump. To date three patients have been entered on this study. One patient received the 72-hour infusion and left the study because of side effects. Two patients received multiple doses of the 24-hour infusion. However, in less than 8 weeks they had progressed.