Rates of small-and large-intestinal calcium transport and their dependence on low doses of vitamin D were compared. Young rats were depleted of vitamin D by feeding a rachitogenic diet for 8–9 weeks; 48 and 24 hr prior to study, half were repleted with 200 IU vitamin D₂. Duodenum and ileum, or cecum and colon, were perfused separately in situ with 1.6 mM calcium and tracer⁴⁵Ca in saline. There was an aboral gradient for net calcium transport and lumen-to-plasma flux with higher values in proximal than distal segments. Vitamin D repletion increased net calcium flux and lumen-to-plasma flux in duodenum and ileum, but not cecum and colon. Plasma-to-lumen flux (calculated as the difference between lumen-to-plasma flux and net flux) tended to be higher in colon than other segments and was not altered by vitamin D repletion.