A relationship between lead retention and vitamin D has been recognized for many years, but the reasons for this association remained unknown. In rats, the manipulation of dietary vitamin D content had no significant effect on the absorption of lead from isolated gut loops and parenteral vitamin D stimulation did not affect lead absorption in rachitic animals. In contrast, dietary vitamin D deficiency and repletion resulted in increased absorption in intact animals due to prolonged gastrointestinal transit time. Both dietary vitamin D deficiency and repletion were associated with decreased body retention of radiolead given intravenously. Further, single doses of parenteral vitamin D administered to animals previously given tracer radiolead resulted in a dose-related enhancement of lead excretion and changes in tissue lead content.