Gastric X-irradiated, achlorhydric rats and sham-operated controls were fed diets containing very soluble calcium chloride or calcium gluconate or slightly soluble calcium carbonate or tricalcium phosphate for 3 weeks. Calcium was absorbed more efficiently by achlorhydric rats from the very soluble salts than from the slightly soluble salts. The control rats absorbed calcium from the very soluble and slightly soluble calcium salts with similar efficiency. Achlorhydric rats fed slightly soluble calcium salts developed weaker bones with a lower mineral content than did those fed very soluble calcium. Apparently, the very soluble dietary calcium offset the impaired calcium absorption of achlorhydric rats. Calcium solubility had no signifcant effect on the bones of control animals.