This review covers recent advances in our understanding of the cell biology and morphogenesis of the ascidian notochord. In its development, the ascidian notochord undergoes a rapid series of cellular and morphogenic events that transform a group of 40 loosely packed cells in the neurula embryo into a tubular column with central lumen in the larva. The ascidian notochord has been a subject of intensive research in recent years, and particular focus in this review will be on events associated with the development and function of polarized cell properties, and the mechanism of lumen formation.