A patient with long-standing, well-controlled polycythemia rubra vera developed recurrent episodes of bullous pyoderma gangrenosum followed by the transformation of his hematologic disease into a rapidly progressive acute myeloid leukemia. This case, together with previously described patients, indicates that the appearance of bullous pyoderma gangrenosum in a patient with polycythemia rubra vera is often of ominous prognostic significance.