The prognostic value of several clinical and hematologic features, recorded at diagnosis, in chronic phase Ph' positive chronic myelocytic leukemia (CML), was analyzed in 135 patients using life-table analysis. About one third of patients were atomic bomb survivors and they had been examined twice a year before the diagnosis of CML. In general, features representing tumor cell burden, i.e., leukocyte count, spleen sizes, and absolute differential cell counts of all granulocyte series cells except myeloblasts affected survival significantly, while sex, age, hemoglobin, platelets, and features representing quality of leukemia, i.e., neutrophil alkaline phosphatase score, percent Ph' positive cells in bone marrow, and percent differentials of all granulocyte series cells except promyelocytes and segmented neutrophils were all insignificant. Multivariate life-table analysis was also performed using age, sex, hemoglobin, platelets, and leukocyte count as predictor variables. The result was that leukocyte was the single most important factor in this analysis and annual death rates between low risk (risk ratio < 0.8) and high risk (risk ratio > 1.4) differed considerably up to four years from diagnosis, indicating our formula to calculate risk ratio is valid as a grading parameter of chronic phase Ph' positive CML within four years from diagnosis.