Plasma acetone turnover rates were measured with the primed continuous infusion of 2-[14C]acetone in patients with moderate to severe diabetic ketoacidosis. Plasma acetone turnover rates ranged from 1.52 to 15.9 μmol · kg−1 · min−1 (108–1038 n,mol · 1.73 m−2 min−1) and were directly related to the plasma acetone concentrations that ranged from 0.47 to 7.61 mM. The average acetoneturnover rate was 6.45 μmol kg−1 min−1 (533 μmol · 1.73 m−2 min−1), a value twice that obtained in a similar group of diabetic ketoacidotic patients via the single-injection technique of 2-[14C]acetone administration. Degradation of urine glucose revealed that 14C from administered 2-[14C]acetone was principally located in carbons 1, 2, 5, and 6 of the glucose molecule in five of six patients. This distribution is similar to that expected from 2-[14C]pyruvate, suggesting that acetone was converted to glucose through pyruvate. In one patient, label was located predominantly in glucose carbons 3 and 4, indicating that acetone metabolism maybe different in some patients. Acetol (1-hydroxyacetone) and 1,2-propanediol (PPD), two possible metabolites of acetone, were detected in plasma of the patients. The concentrations of Acetol ranged from 0 to 0.48 mM and of PPD ranged from 0 to 0.53 mM. The concentrations of each metabolite were directly related to the plasma acetone concentrations. During the continuous infusion of 2-[14C]acetone, the specific activities of plasma glucose and PPD rose continuously but did not reach constant values. Estimates of theminimal percent plasma glucose and PPD derived from plasma acetone averaged 2.1 and 74%, respectively.