The objective of this experiment was to determine calcium (Ca) balance and the kidney content of Ca in young male Wistar, Fischer, Sprague-Dawley and Donryu rats fed a high-phosphorus (P) diet in the form of Harpers' salt. During the three weeks of the experiment, each of the four rat strains was fed a diet containing either 0.5% or 1.5% P, and urine and fecal samples were collected in the final week. Food intake in all strains was significantly decreased by the high-P diet, and food intake differed among the strains. The effect of the high-P diet on Ca utilization showed that the Ca balance was not significantly modified in Wistar and Sprague-Dawley rats, but Ca absorption and retention were significantly increased in Fischer rats and significantly decreased in Donryu rats. The kidney content of Ca in all strains was significantly increased by the high-P diet, and the kidney Ca content varied among the strains. The effects of dietary P on Ca utilization cannot always be duplicated among different rat strains, but an increase of calcification can be promoted by a decrease of food intake. We suggest that the effect of high dietary P on Ca utilization is closely related to a decrease of food intake.