In order to determine the influence of laboratory procedures on nutrient values in different food tables and data banks, an interlaboratory study was set up. Nineteen laboratories participated, and received well-homogenized samples of egg powder, full-fat milk powder, whole rye and wheat meal, biscuits and french beans to perform analyses of macronutrients by their own routine methods. For dry weight the results agreed very well; the results for ash agreed rather well. For protein the coefficient of variation between laboratories (CVbetween) ranged from 2.8% to 6.4%. The CVbetween for total fat ranged from 5.4% to 54%. For available carbohydrates the CVbetween ranged from 9% to 27%. The CVbetween for total dietary fiber ranged from 23% to 84%. It is concluded that leading laboratories produce widely different values for macronutrients in common foods. Reference materials of certified nutrient concentration are needed.