Accumulating evidence suggests a relationship between mild hyperoxaluria and "idiopathic" calcium oxalate renal lithiasis. Studies on oxalate excretion in these patients has been limited by the absence of a reliable method for measuring urinary oxalate. Methods currently in existence either require extensive purification of urine, or are relatively imprecise. Preliminary experiments performed by us indicate that the technique of conductivity chromatography can be applied to the direct and precise measurement of oxalate in urine. The objective of this proposal is to characterize the technique of measuring oxalate by conductivity chromatography. Once the technique has been perfected, it will be applied to clinical studies of oxalate excretion. We will device an oxalate tolerance test to screen for absorptive hyperoxaluria in patients with oxalate lithiasis. In addition, we will investigate the proponderance of oxalate lithiasis in males by determining the effect of changes of plasma testosterone concentration on urinary oxalate excretion.