Reduction mammoplasty tissue was used to obtain short-term cultures of human epithelial cell populations. Digestion of tissue with collagenase and hyaluronidase resulted in cell clusters (organoids) resembling ductal and alveolar structures; these could be separated by filtration from the stromal components. Epithelial outgrowth from these organoids was greatly enhanced by the addition of conditioned medium from other human epithelial and myoepithelial cell lines. Additionally, the mammary epithelial growth was stimulated by insulin, hydrocortisone, epidermal growth factor, and steroid hormones. With this enriched nutritional environment, active cell division could be maintained for 1 to 3 months and cells could be serially subcultured 1 to 4 times.