1. The renal clearance of oxalate was studied in six normal subjects and in two patients with primary hyperoxaluria utilizing a constant infusion of [14C]oxalic acid.
2. The [14C]oxalate clearance in normal subjects was between 101 and 217 ml/min with a range in the ratio of [14C]oxalate clearance to creatinine clearance of 1.33–2.09.
3. The oxalate clearance in two patients with primary hyperoxaluria was within the range found in the normal subjects.
4. This study does not confirm the previous report of a low oxalate/creatinine clearance ratio in man nor the finding of an elevated oxalate clearance in patients with primary hyperoxaluria.
5. Estimates of serum oxalate concentration based on these clearance values suggest that the serum oxalate concentration in normal subjects is less than 100 μg/100 ml.