The effects of moderate increases in dietary calcium on maternal and foetal mineral interactions were studied in Charles River CD/VAF Plus rats. Female rats were given 0.50, 0.75, 1.00 or 1.25% dietary calcium as calcium carbonate in AIN-76A diets for 6 wk before mating, during mating and for 20 days of gestation. Inductively coupled argon plasma-atomic emission spectrometry was used to determine mineral levels in the tissues of non-pregnant rats after 42 days on the diets, in the tissues of pregnant rats on day 20 of gestation and in the whole body of day-20 foetuses. The femurs of the non-pregnant and pregnant rats had a dose-related linear increase in calcium content. In livers of the non-pregnant rats, dose-related linear increases in the phosphorus, zinc and magnesium content were observed, but there was a dose-related decrease in the iron content. There were dose-related linear decreases in the iron and copper contents of the kidneys from the non-pregnant rats. In pregnant rats dose-related linear decreases were observed in the iron content of the liver and in the zinc, iron and magnesium contents of the kidney. The foetuses from rats given a moderate increase in dietary calcium had dose-related decreases in the whole-body contents of phosphorus, iron, copper and magnesium.