Triacetin, the water‐soluble triglyceride of acetate, was infused in mongrel dogs at isocaloric (N=6) or hypercaloric (~1.5 REE, N =7) rates in mongrel dogs for 3 hr. Ketone body and glucose production rates were quantified with [13C2] acetoacetate and [3H]glucose, respectively. Four additional animals were infused with glycerol to serve as controls for the hypercaloric triacetin infusion. Energy expenditure was determined in the isocaloric experiments. Results: no evidence of acute toxicity was observed during triacetin infusion at either rate. Plasma acetate concentrations increased from basal levels to ~1 and ~13 mmol/liter in the isocaloric and hypercaloric experiments, respectively. Plasma lactate and pyruvate concentrations decreased dramatically after 30 min of both isocaloric and hypercaloric triacetin infusions. Glucose production rates did not increase in either group, but glucose clearance decreased significantly in both groups (p<0.05) over the last hour of triacetin infusion. Plasma ketone body concentrations increased from 1.4 to 3.5 and 1.8 to 13.5 μmol/kg·min, respectively, during isocaloric and hypercaloric triacetin infusion. Resting energy expenditure increased from 3.0 ± 0.3 to 4.0 ± 0.5 kcal/kg·hr during isocaloric triacetin infusion (p<0.05). These studies indicate that triacetin can be administered to dogs at high rates without overt toxicity. The decrease in glucose clearance may represent competition between carbohydrate (glucose) and lipid (acetate). Triacetin infusion resulted in significant increases in ketone body production and concentration. These preliminary data indicate that triacetin may have a future role as a parenteral nutrient, and that further studies of its use are warranted.(Journal of Parenteral and Enteral Nutrition15:32–36, 1991)