Twenty-one glycogen-rich clear cell carcinomas of the breast were studied. There were 13 invasive carcinomas and 8 intraductal carcinomas. Ten of the invasive carcinomas contained an intraductal component. Three intraductal carcinomas were papillary carcinomas ("intracystic" papillary carcinoma), and the others showed a mixture of solid, micropapillary, and cribriform patterns of growth. Most of the invasive carcinomas had nested, corded, or sheet-like growth patterns, and all were grade 2 or 3 neoplasms. Among patients with invasive carcinoma, two had metastases to axillary lymph nodes and three died of tumor. One patient with intraductal papillary carcinoma experienced two local recurrences, with invasion in the second recurrence. Thirteen cases (62%) exhibited focal apocrine features. Based on this small series, the clear cell morphology did not appear to influence the clinical outcome once stage and grade were taken into account. Glycogen-rich clear cell carcinoma of the breast may be a variant of apocrine carcinoma.