Summary. Sweet's syndrome (SS) developed in two patients with acute myeloid leukaemia (AML) treated with granulocyte colony stimulating factor (G-CSF) for febrile neutropenia due to AML chemotherapy. Fever, painful skin and conjunctival lesions developed and neutrophilic infiltration was detected at biopsy specimens. Neutrophilia was not detected. Skin lesions regressed within 1–2 weeks and conjunctival lesions within 4 weeks following the cessation of G-CSF. We conclude that SS may be a complication of G-CSF therapy and tender skin and/or conjunctival lesions developing during G-CSF therapy should suggest the possibility of SS.