Abstract
The reciprocal crosses between Pseudogobio esocinus and Biwia zezera are successful and three hybrids from P._??_B._??_are reared until they reach one-year age with a survival rate similar to that of controls. The hybrids are not only intermediate morphologically, but also they behave intermediatelly between their parental forms. Of three hybrids reared until one-year age, two are sterile males and remaining one is a neuter. None of spermatozoa is observed in their testes.
