The sensory epithelium of the mammalian cochlea, the organ of Corti, is comprised of ordered rows of cells, including inner and outer hair cells. Recent results suggest that physical changes in the overall size and shape of the cochlear duct, including possible convergence and extension, could play a role in the development of this pattern. To examine this hypothesis, changes in cell size and distribution were determined for different regions of the cochlea duct during embryonic development. In addition, changes in the spatial distribution of sensory precursor cells were determined at different developmental time points based on expression of p27kip1. Unique changes in luminal surface area, cell density, and number of cell contacts were observed for each region of the duct. Moreover, the spatial distribution of p27kip1-positive cells changed from short and broad early in development, to long and narrow. These results are consistent with the hypothesis that convergence and extension plays a role in cellular patterning within the organ of Corti. Developmental Dynamics 229:802–812, 2004. Published 2004 Wiley-Liss, Inc.