Fifty-four patients aged 60 years or older with a diagnosis of chronic myelogenous leukemia were referred to University of Texas M. D. Anderson Hospital between 1965 and 1982. Patients in this age group had a significantly shorter median survival than that of the 249 patients younger than 60 seen during the same period (26 vs 42 months; P = .01). Old age was associated with a higher incidence of poor performance status, hepatomegaly, and anemia. Fourteen other patient characteristics were correlated with poor prognosis, including black race, weight loss, symptoms, hepatomegaly, splenomegaly, anemia, thrombocytopenia or thrombocytosis, increased peripheral blast cells and promyelocytes or basophils, increased blasts or basophils in the bone marrow, decreased megakaryocytes, and additional cytogenetic abnormalities. A multivariate analysis that accounted for the interactions of these factors identified old age as being of primary adverse prognostic significance in patients with chronic myelogenous leukemia, suggesting a biologic difference in the disease in older patients. The poor prognosis in elderly patients receiving present available therapy justifies promising and well tolerated investigational approaches such as interferons in patients in this age group.