Abstract 1. 1. The expression of LDH genes throughout early development of different Xenopus species, and interspecies hybrids has been compared. 2. 2. In X.1. victorianus oocytes the LDH-B 4 polymer is synthesized exclusively and is stored during early embryonic stages. For the first time at stage 27 is the embryonic LDH gene activity manifest. 3. 3. In other species the situation is somewhat more complicated, in that additional anodal bands appear or, like in X. clivii, even cathodal polymers are formed. 4. 4. In X.1. victorianus ♀ × X. borealis ♂ hybrids only the maternal pattern was expressed throughout the whole embryonic development. This allelic repression persisted up to metamorphosis.