Increased and deregulated expression of glucose transporters is a characteristic of cancer cells. We previously identified a novel glucose transporter protein, GLUT12, in the MCF7 malignant breast epithelial cell line. Here we present the first demonstration of GLUT12 expression in human breast tumours. Using immunohistochemistry and reverse transcription polymerase chain reaction, GLUT12 was detected in eight of ten invasive tumours. Ductal cell carcinoma in situ cells also stained strongly for GLUT12. Immunohistochemical staining for GLUT12 in benign ducts was less intense, with few positively stained cells. GLUT12 may have a role in hexose supply to breast cancer cells.