The effect of oral administration of Crataeva nurvala bark decoction on calcium oxalate lithiasis has been studied in rats. The elevation of the oxalate-synthesizing liver enzyme, glycolate oxidase, produced by feeding glycollic acid was remarkably reduced with the decoction, showing a regulatory action on endogenous oxalate synthesis. Protein-bound carbohydrates were increased in the renal tissues during calculosis but these changes were not reversed with the herbal treatment. The increased deposition of stone-forming constituents in the kidneys of calculogenic rats was lowered with decoction administration. The increased urinary excretion of the crystalline constituents along with lowered magnesium excretion found in stone-forming rats was partially reversed by decoction treatment.