Several studies indicate that interferon (IFN) treatment, intensive chemotherapy and autologous bone marrow transplantation (ABMT) effectively reduce the Ph-positive clone in Chronic Myelogenic Leukemia (CML). In the present study on patients < or = 55 years, we have combined these three treatment modalities. The aim of the study was to eliminate or minimize the Ph-positive clone to see whether a status of minimal residual or Ph-negative disease could be maintained for a longer period of time. After diagnosis, patients received interferon (IFN-a-2b) and hydroxyurea (HU) to keep the white blood cell (WBC) and platelet count below 2-4 and 100-150 x 10(9)/l, respectively. After six months of treatment, Ph-analysis was performed. Patients with Ph-positive cells in bone marrow then received 1-3 courses of intensive chemotherapy. In patients Ph-negative after two courses, bone marrow was harvested and used for ABMT. After a third course, patients with up to 50% Ph-positive metaphases were accepted for ABMT. As of January 1, 1993, 97 patients were registered in the study. Six months of IFN+HU reduced the percentage of Ph-positive metaphases in 57% of the patients (7% became Ph-negative). The corresponding figures after two intensive cytotherapies were 70% (40% Ph-negative). Eighteen patients were autotransplanted. Seven have relapsed with Ph-positivity 3-22 months after ABMT, while nine are Ph-negative at 1-32+ months after ABMT (two not yet analyzed). Seventeen patients are alive and well, while one died one month after ABMT due to interstitial pneumonia.(ABSTRACT TRUNCATED AT 250 WORDS)