The case of a patient with a history of polycythemia vera and 46,XX karyotype who transformed into acute nonlymphocytic leukemia with 46,XX,t(1;3)(p36;q21) rearrangement is reported. Significant percentages of the circulating blasts in the peripheral blood were positive on immunocytochemical stains for megakaryocyte markers, anti-Factor VIII, and antiglycoprotein IIb/IIIa. On the basis of our studies and published reports, trilineage hematopoietic abnormalities and a poor response to therapy may represent typical features of patients with t(1;3).