The chronic oral toxicity of erythritol was examined by feeding erythritol at dietary levels of 0 (controls), 2, 5, or 10% to groups of four male and four female dogs for 53 weeks. Erythritol was well tolerated at all dose levels without evidence of diarrhea. Water consumption was slightly higher in the high-dose group than in controls. Body weights and weight gains were not affected by treatment. There were no clinically relevant changes in hematological or clinicochemical parameters attributable to treatment. In particular, plasma electrolyte concentrations remained unaffected. Evaluation of a number of urinary parameters (including electrolytes and renal enzymes) was hampered by widely varying urine volumes among individual dogs; however, the available data did not indicate treatment-related effects on the urinary excretion of electrolytes (K+, Na+, Mg2+, and Pi) or enzymes (gamma-glutamyltranspeptidase, N-acetyl glucosaminidase, and lactate dehydrogenase). Quantitation of erythritol in the urine demonstrated that 50 to 80% of the ingested dose was absorbed and excreted in the urine. Analysis of terminal organ weights did not reveal treatment-related differences. No histopathological changes attributable to treatment were observed in the kidneys or in any other organ or tissue examined. It was concluded that daily erythritol consumption of up to 3.5 g/kg body wt was well tolerated by dogs.