This 3 week 3 period crossover study compared the effects of 3 diets with varying levels of fibre and macronutrients on postprandial plasma glucose, triglyceride, free fatty acid, and insulin concentrations over a 12 hour period in 12 healthy lean neutered dogs. Plasma was analysed prior to and after a meal and the end of the third week of each test period. The moderate carbohydrate and fibre diet resulted in postprandial glucose concentrations 0.4- 0.7 mmol/l lower than for both higher carbohydrate diets. Postprandial glucose, insulin, and triglyceride concentrations did not return to baseline by 12 hours postprandially for each of the three diets in some dogs. These results show that a moderate carbohydrate and fibre diet should be further investigated in diabetic dogs. Plasma levels of glucose and other analytes should be measured over at least 12 hours postprandially.