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.