The present and suggested stage and substage divisions of the Wanganui Series are discussed and stratigraphic sections in Wanganui, Hawke' Bay, southern Waira-rapa, and North Canterbury are reviewed to determine the ranges of molluscs formerly used to define stages and substages. It is concluded that the Opoitian, Waipipian, Mangapanian, Nukumaruan, and Castlecliffian are recognisable stages, and the Okehuan and Putikian are recognisable substages of the Castlecliffian Stage.