Although leiomyomas (LMs) of the uterus are common, hematopoietic components within these tumors are not. Lymphoid and other hematopoietic elements have been previously recognized, but eosinophilic infiltrates in LMs have received little attention in the literature. The clinical and pathologic features of 3 cases of uterine LM with eosinophilic infiltration were studied. The patients ranged in age from 35 to 62 years and presented with abdominal and/or pelvic pain and abnormal uterine bleeding. None had peripheral blood eosinophilia or clinical evidence of allergy or parasitic infection. One patient had a benign LM, and the other 2 patients had smooth muscle tumors of uncertain malignant potential. The tumors contained variable numbers of eosinophils and Giemsa stains showed variable numbers of mast cells in addition to the eosinophils. We also performed immunohistochemical and in situ hybridization studies to assess for interleukin-5 (IL-5) and eotaxin in these LMs. There was no consistent association between the presence of eosinophils and either IL-5 or eotaxin in smooth muscle cells, suggesting that mechanisms other than IL-5 or eotaxin production may account for the eosinophilia. Because eosinophils are believed to be involved in wound healing, tissue remodeling, and fibrosis, their presence within LMs may reflect a response to tissue injury produced by the neoplasm rather than intrinsic recruitment by chemotactic factors produced by the smooth muscle cells. Their presence, however, does not appear to have any clinical significance.