Calcium oxalate is a major component of renal stones, and its urinary concentration plays an important role in stone formation. Even a small increase in urinary oxalate has a significant impact on calcium oxalate saturation. Although primary hyperoxaluria is relatively uncommon, patients with calcium oxalate stones have some degree of hyperoxaluria. To understand the underlying causes of such hyperoxaluria, the processes of oxalate synthesis and excretion must be clarified. This article focuses on the determination of oxalate, calculation of its saturation, and the hyperoxaluric syndromes with special reference to metabolic precursors of oxalate, including ascorbic acid, glyoxylate, and glycolate.