Two subjects with Ph-positive chronic myeloid leukemia (CML) in whom pustular Sweet's syndrome was diagnosed are reported. The first patient was a 47-year-old woman who developed fever, painful ulcers of the oral mucosa and vagina and generalized pustulous skin lesions 2 years after the diagnosis of CML. Histologically, the skin lesions consisted of dense neutrophilic infiltrates with perifollicular disposition. The microbiologic studies were negative. The lesions showed a favorable response to corticosteroids, but fever recurred with every attempt of tapering prednisone; it finally disappeared with the addition of oral cyclophosphamide. The second patient was a 45-year-old man who developed fever and disseminated pustules with histologic features consistent with Sweet's syndrome and negative microbiologic studies at 2.5 years after diagnosis of CML. The picture showed a dramatic response to prednisone and did not recur after the drug was discontinued. In both patients, CML remained stable after resolution of Sweet's syndrome.