Survival of patients with chronic myeloid leukemia seen in the University of Colorado Leukemia Clinic were reviewed with respect to therapy. A total of 55 patients seen consecutively through mid 1980 were included in this study. Of these patients 30 were treated with busulfan, 14 were treated with hydroxyurea and 11 received under modalities. Busulfan treated patients who are now deceased, have had a median survival of 35 months (range, 13-108) and actuarial analysis shows the total busulfan treated population to have an expected median survival of 48 months. Hydroxyurea treated patients who are still alive have been followed for a median period of 69 months (range, 25-136 months) and a projected median survival for periods of 56 and 90 months, respectively. These data suggest that hydroxyurea may be an important treatment modality in the treatment of chronic myelogeous leukemia.