1. In eight Dalmatian dogs low and high purine intakes resulted in plasma urate levels from 25 to 185 mumol/l. 2. The relationship between purine intake and excretion of uric acid and allantoin per day was described by linear regression equations. 3. The elimination of endogenous purines was 1.8 mmol/day for urate and 1.7 mmol/day for allantoin. Exogenous purines increased renal excretion by 0.57 mmol/mmol. 4. Kinetic measurements with [2(-14)C]uric acid infused continuously into each of two dogs on low and high purine revealed increases of plasma pool (urate + allantoin) of 3.3 fold and entry rate of 4.0 fold. Conversion of urate into allantoin increased from 20 to 36%. 5. Renal elimination of catabolites increased 3.3 fold and exhalation rate of purine-CO2 379 fold. Extra-renal elimination at high purine intake was quantitatively similar to humans and closely related to pool size.