Angiotensin-I converting enzyme (ACE) is involved not only in intracellular volume regulation but also in proliferation control. Since both ACE gene polymorphism (I/D ACE) and ABO blood group determine ACE level in peripheral blood and probably also in bone marrow, the hypothesis to the interindividual differences in survival of leukemic patients was suggested. The data of 25 patients of both sexes with acute myelogenous (AML), acute lymphatic (ALL), chronic myelogenous (CML) and chronic lymphatic (CLL) leukemia treated by conventional were used for the study. The overall survival (SUR) was estimated as the time from the date of diagnosis to the date of death. The difference between patient's individual SUR (iSUR) and median SUR according to the type of leukemia (mSUR) was calculated. This difference (iSUR-mSUR) varied with I/D ACE genotype (p<0.02) but neither with diagnosis nor with ABO blood group. The regression model for iSUR calculation, from mSUR and I/D ACE genotype, has been suggested.