A family with erythroleukemia is presented, in which father and son were diagnosed at the same age, but 20 years apart, with almost identical clinical and morphological features of the disease. No environmental factors were identified. The karyotypic abnormalities of the bone marrow blasts in the son demonstrated 2 major clones, involving chromosomes 5 and 7, as well as 8, 13, 16 and 21. Both patients demonstrated a poor response to chemotherapy. Previously described families with erythroleukemia are reviewed with available specific karyotypic aberrations.