Enteric hyperoxaluria complicates extensive disease or resection of the small intestine in the presence of an intact colon, and is associated with calcium oxalate nephrolithiasis. In addition to hyperoxaluria these patients have a low urine volume, low urinary ionic strength and hypocitraturia. Many forms of treatment have been recommended, but none has been subjected to a prospective clinical trial. Mild idiopathic hyperoxaluria is reported in 8-50% of idiopathic calcium oxalate stoneformers. Several pathophysiological mechanisms have been proposed, including low dietary calcium and possible oxalate transport defects in the gut and/or the kidney. Mild hyperoxaluria, or a high oxalate:calcium ratio in the urine, may be particularly important risk factors for calcium oxalate stone formation; an approach to the correction of these abnormalities is proposed.