Although symmetrical and asymmetrical divisions of stem cells have been extensively studied in invertebrate and mammalian neural epithelia, their role remains largely unknown in mammalian non-neural epithelial development, regeneration and tumorigenesis. Here, using basal and luminal cell-specific markers and cell lineage tracing transgenic mice, we report that in developing prostatic epithelia, basal and luminal cells exhibit distinct division modes. While basal cells display both symmetric and asymmetric divisions leading to different cell fates, luminal cells only exhibit symmetrical divisions. Examination of cell division modes in prostate-specific Pten-null mice indicates that both luminal and basal cells can be cellular origins for prostate cancer. Furthermore, analysis of Sox2-expressing cells in p63 and Pten-null mice suggests that basal cells contribute to the luminal population and tumorigenesis. These findings provide direct evidence for the existence of a hierarchy of epithelial cell lineages during prostate development, regeneration and tumorigenesis.