Fungal infections of the breast are unusual and may clinically mimic carcinoma. When studied by fine-needle aspiration (FNA), such masses may yield necrosis, granulomatous inflammation, reactive histiocytes, and atypical epithelial cells. Cohesive groups of atypical epithelial cells featured nuclear enlargement and overlapping, as well as prominent nucleoli. The organisms may be widely scattered, so that careful evaluation was required for their identification. In concert with provocative clinical findings, these features may lead to an erroneous diagnosis of malignancy. We describe three women with mycotic masses of the breast initially studied by FNA. The first patient presented at age 31 with a large, firm breast mass, chest wall extension, and radiographic evidence of vertebral bone involvement. FNA was requested to confirm the clinical diagnosis of advanced breast carcinoma. In addition to the atypia described above, the smears showed yeast forms indicative of blastomycosis surrounded by neutrophils. She remains well, following antifungal treatment. The second case of Blastomycosis was diagnosed by FNA of a breast mass in a 64-yr-old woman, who also responded to treatment. The third patient's preoperative needle aspiration showed granulomas, but no organisms were identified, even with special stains; silver stains of surgically excised tissue showed histoplasmosis.