Pearl color and weight were investigated by transplanting mantle tissue from specimens selected for white shell color in the prismatic layer in order to obtain information for selective breeding of the Japanese pearl oyster Pinctada fucata martensii. The frequency of yellow pearls was significantly lower in the group produced by grafting mantle tissue from the inbred white line than from brown lines in two experiments. Pearl weight did not differ between the two groups produced by grafting mantle tissue of white or brown types of donor. Positive correlation was observed between the weight of pearls and that of the shell of host oysters. These results have implications for the selective breeding of host and donor pearl oysters.