The ability of Red-legged frog (Rana aurora) tadpoles to discriminate between siblings and non-siblings was investigated in laboratory choice experiments. Tadpoles that were reared with siblings only and tested in early developmental stages preferentially associated with siblings over non-siblings. Animals reared with siblings only and tested in later developmental stages did not preferentially associate with siblings over non-siblings. Test animals that were reared in isolation, those reared with siblings and non-siblings, or those reared with non-siblings only, displayed a random association among sibling and non-sibling stimulus choice groups. These results are compared with results obtained from testing the larvae of a closely related species, the Cascades frog (Rana cascadae).