Fifty-seven patients with advanced breast cancer were treated with a combination of 5-fluorouracil and mitomycin C (FuMi). Fifty-three were previously treated with hormones and/or cytotoxic drugs. Complete and partial remissions (CR, PR) were seen in 16%, stationary disease in 46%, and progressive disease in 38%. The mean time to remission was 4.5 (CR) to 4.0 (PR) months. The toxicity was mild and consisted mainly of thrombocytopenia. The FuMi-regimen may be a useful alternative in advanced breast cancer, at least in progression after previous systemic therapy, and if a moderate toxicity is considered important.