This paper analyzes factors affecting the choice of a reference amount in nutrition labeling. Two most common reference units are compared: a serving and 100 grams; advantages and shortcomings are discussed; implications for policymakers are drawn. Choice of a reference unit is often dictated by existing labeling traditions and the prevailing system of measurements. The authors recommend that international harmonization of food labeling be based on general principles that allow flexibility rather than provide specific recommendations on the label components and format. This way countries can preserve and further the labeling traditions to which consumers have become accustomed.