The pearl oyster Pinctada fucata martensii is the dominant species for production of marine pearls in China. To explore the relative contributions of donor and host oysters to nacre deposition in cultured pearls, donors of 3 size groups—large, medium, and small—and hosts of different sizes were used for pearl production. Resulting pearls were numbered to allow tracing of donor and host. Results showed that pearls developed from the 3 different groups of donors showed no significant difference in diameter, weight, and nacre thickness; however pearls cultured in different-size hosts differed significantly with regard to these parameters. Specifically, pearl size, weight, and nacre thickness correlated positively with the size and weight of host oysters, with coefficients ranging from 0.22–0.34. It is suggested that in selection of host oysters used for pearl production, if other conditions are equal, those of larger size and weight are more preferable, for they will presumably produce pearls of larger size and nacre thickness.