Male weanling tats were fed an adequate diet supplemented with 0.42% P from either hexametaphosphate or orthophosphate, each at two levels of Ca intake (0.53% or 1.06%). Polyphosphates represented 13% of the total fecal phosphorus at the 0.53% Ca intake; this fraction was increased to 27% at the 1.06% Ca intake. Hexametaphosphate caused a 15% increase in fecal iron, a 12% decrease in liver iron and a 15% decrease in fecal zinc losses. These effects were markedly enhanced by supplemental Ca. Orthophosphate was without effect at the 0.53% Ca intake, but caused an 11% increase in fecal zinc losses at the 1.06% Ca intake.