We report a rare case of eosinophilic leukemia transformation in a patient with polycythemia rubra vera on hydroxycarbamide (hydroxyurea) therapy only. Cytogenetic study showed complex abnormalities including -5, -7, +8, suggestive of a secondary leukemia. The leukemogenic risk of hydroxycarbamide, a ribonucleoside reductase, and the risk of natural leukemic transformation of polycythemia rubra vera is discussed in the context of previous PVSG studies.