The effects of calcium (Ca) carbonate and bovine bone powder (BBP) as dietary calcium sources on Ca metabolism in plasma and bone of vitamin D-deficient rats were investigated. The rats were fed ad libitum on a diet with a high Ca content (1.2%) adjusted with either Ca carbonate or BBP under vitamin D-deficient or -replete conditions for 28 days. During and after feeding, the concentrations of Ca, phosphorus, 25-hydroxyvitamin D₃ (25-OH-D₃) and alkaline phosphatase activity in plasma were measured. Furthermore, femoral bone length, width, weight, strength, Ca and phosphorus contents and mineral density were determined. Under vitamin D repletion, both BBP and Ca carbonate significantly enhanced Ca metabolism in plasma and bone, and there was no significant difference between the bioavailabilities of both Ca compounds in plasma and bone Ca metabolism. In contrast, under vitamin D deficiency, BBP enhanced plasma and bone Ca metabolism in a similar manner to that observed in vitamin D repletion. On the other hand, Ca carbonate showed weaker effects on plasma and bone Ca metabolism than BBP. These results suggest that BBP could be an effective dietary Ca source.