Imatinib mesylate blocks bcr/abl kinase activity effectively, and thus is a promising drug in Philadelphia chromosome positive leukemias. While under imatinib treatment high hematological and cytogenetic response rates could be observed, usually only mild non-hematological side-effects like skin rash, edema, and muscular cramps occur. Here we report two severe cases of acute generalized exanthematous pustulosis due to imatinib. In both patients the generalized pustular eruptions could be observed 12 wk after initiation of imatinib treatment. Numerous microbiological investigations excluded an infectious etiology, and histopathology of cutaneous lesions was consistent with acute generalized exanthematous pustulosis. Accordingly, withdrawal of imatinib led to a restitutio at integrum of the integument. Our report confirms another single observation of acute generalized exanthematous pustulosis in chronic myeloid leukemia under imatinib therapy, and confirms that this is a rare but proven adverse effect of imatinib.