Changes in plasma urea and creatinine concentrations were compared in 6 dogs fed 3 meals (cooked meat, raw meat, and a soft-moist preparation) in a crossover fashion. Each meal produced changes in urea and creatinine values. Although increased urea values were seen after all meals, the effects on creatinine were varied; concentrations increased after feeding cooked meat, but decreased after consumption of raw meat or soft-moist food. Although the creatinine changes were less pronounced, the variable effect of diet complicates the interpretation of plasma creatinine concentration in evaluating renal function.