This report describes three patients with chronic myelogenous leukemia who developed gastric antral vascular ectasia (GAVE) during treatment with imatinib mesylate (IM). Cessation and/or switching from IM to nilotinib resulted in the alleviation of gastrointestinal (GI) bleeding and ectatic lesions. Furthermore, GI bleeding recurred after the re-administration of IM in one patient. Thus, we consider that the occurrence of GAVE in our patients was induced by IM. Although the precise mechanism of IM-GAVE is not understood, all patients took at least 400 mg/day of IM at the onset of GAVE. Thus, higher doses of IM (≥400 mg/day) may be a risk factor for IM-GAVE.