In this paper, we report chemical structures of five compounds including four novel polyhydroxylated cardiac steroids in the eggs of a toad, Bufo marinus. These cardiac steroids were purified by high-performance liquid chromatography, and their structrues were determined to be 11α, 19-dihydroxytelocinobufagin (I), 11α-hydroxytelocinobufagin (II), 11α, 19-dihydroxymarinobufagin (III), 11α-hydroxymarinobufagin (IV) and 19-hydroxytelocinobufagin (V) on the basis of spectral data of nuclear magnetic resonance and mass spectroscopy. All the five compounds showed biological activity, as tested by inhibition of Na⁺, K⁺-ATPase activity and of [³H]ouabain binding to the receptor on Na⁺, K⁺-ATPase. This is the first finding of bufadienolides as cardiac steroids in animal eggs.