Aspects of breeding biology, larval development rates and temperature tolerance, and adult respiratory physiology of the hylid frogsLitoria raniformisandL. ewingiare compared. In Canterbury, the green frogL. raniformisbreeds in spring and summer and disappears in winter. Its larvae survived well in the laboratory at 23 ± 2°C but mortality was high at 15 ± 3°C. In contrast, the whistling frogL. ewingibreeds throughout the year in the South Island, and tadpoles had excellent survival at both temperatures.L. raniformishad a larval life-span of greater than 70 days at 23 ± 2°C, whereas mostL. ewingicompleted metamorphosis 50–64 days after hatching, at this temperature. During metamorphic climax ofL. raniformis, head-plus-body length remained nearly constant whilst the tail was resorbed, contrary to a previous report. At 23°C in the laboratory, adultL. ewingiand juvenileL. raniformisof the same size remained alert and had similar rates of oxygen consumption. However, at 7°CL. raniformisbecame torpid and the mean rate of oxygen consumption was significantly lower than that ofL. ewingi.These differences appear at least partially attributable to a relative independence of the effects of cold temperature on pulmonary and buccopharyngeal ventilation frequencies inL. ewingi.