The size, weight and sexual structure of Pelophylax ridibundus and Bombina bombina populations was analyzed during their spawning migrations in 2013 - 2015 in four lakes of the Medveditsa River flood-plane (Saratov Region, Lysogorsky District). The body length of Pelophylax ridibundus males ranged from 29.3 to 101.3 mm (the weight from 2.10 to 152.2 g), and that of females did from 36.1 to 120.2 mm (the weight from 4.45 to 181.0 g); for Bombina bombina males - from 25.4 to 50.6 mm (the weight from 1.06 to 8.5 g), and that of females from 32.1 to 49.7 mm (the weight from 2.64 to 8.43 g).