This study has examined the fertility rate. the viability and the incidence of heteroploidy of each group of Japanese quails divided by their dam body weight and sire body weight Using 1,349 early embryos of the Japanese quails which were selected and bred for the levels of total plasma phosphorus. As regards the dam body weight. the DBW3 group whose dam body weight was the heaviest produced more heteroploidy than the DBWl or DBW2, but with regard to the sire body weight. the SBWl or SBW2 whose sire body weight was lighter produced more heteroploidy than SBW3 whose sire body weight was heavier.