We investigated the influence of chronic exposure to four different concentrations of salinity (NaCl) on survival of larval Northern Leopard Frogs (Rana pipiens) across 24 d. We also assessed if corticosterone mediates lethal effects of NaCl by inhibiting actions of corticosterone for half of the larvae in each treatment using mifepristone (a glucocorticoid antagonist). The dataset contains survival data (percent of larvae surviving) per group and day