The aim of the study is to report the long-term outcome and secondary tumours of early breast cancer patients of adjuvant CNF (cyclophosphamide, mitoxantrone, and 5-fluorouracil) chemotherapy. One hundred and ninety four patients, 185 primary early breast cancer and nine locoregionally recurrent breast cancer patients, were entered onto the trial between May 1986 and November 1993. The therapies included surgery, radiation therapy, adjuvant CNF chemotherapy, and tamoxifen according to hormonal status. Some of patients were treated twice with CMF (methotrexate). The median follow-up time was 12.9 years. Eighty nine (48%) primary breast cancers relapsed, and six locoregional breast cancers relapsed. After 5-10 years the relapse incidence decreased notably. Eighty three patients died of breast cancer, and nine of other causes. Two cases of leukemia, six cases of skin cancer, two cases of Hodgkin's disease, two cases of meningioma, and two cases of endometrial cancer were observed. This article confirms the feasibility of adjuvant CNF for early breast cancer patients. Questions of possible causability of secondary cancer have yet to be explored.