Effects of dietary phosphate levels and phosphate sources on iron utilization were studied. Seventy-two Wistar-strain male rats (70g body weight) were divided into 12 groups. Each group was fed one of four phosphate sources, either KH2PO4, K5P3O10, NaH2PO4 or Na5P3O10, and the diet was supplemented to approximately 0.5%, 1.0% or 1.5% P. Results: 1) The high dietary phosphate level (1.5%) resulted in significant decreases in weight gain, food intake and nitrogen retention. 2) Absorption and retention of Fe decreased, and urinary excretion increase, with increasing P intake by K2P3O10 and Na5P3O10 feeding.