The planktonic foraminiferal biostratigraphy of cores 22-45 from DSDP Site 593 (Challenger Plateau, Tasman Sea) is related to New Zealand onshore Miocene stages (Altonian-Tongaporutuan). An excellent succession of Altonian events at the site allows the stage to be divided into three informal zones. Upper Clifdenian and some lower Lillburnian horizons are highly condensed, or missing; this possible hiatus near 393.5 m is at a prominent litho-stratigraphic boundary. A pronounced increase in representation of dextrally coiled Globorotalia miotumida immediately above the base of Tongaporutuan Stage in two onshore sequences is also recorded at Site 593. It may provide a useful criterion for the boundary in oceanic sequences lacking the Bolivinita quadrilatera group, as well as defining a basal Tongaporutuan zone. The highest occurrence of Globoquadrina dehiscens near the top of core 28 is well defined and possibly provides a useful intrastage event.