In eight Dalmatian dogs exogenous effects (dietary purine, xylit infusion) on plasma uric acid were examined and relationships between purine intake and excretion were established. Increasing purine intake resulted in a linear increase in renal excretion of urate (r = 0.952) and a less steep increase of allantoin (r = 0.901). In pairs of two animals with low and high purine intakes the metabolic fluxes in steady state were measured by continuous infusion of (2-14C) urate. The extrarenal excretion rates of urate + allantoin during high-purine and low purine feeding averaged 2.9% and 8.5% of entry rates. The results are discussed in comparison with human data and a remarkably good agreement is observed.