In 1987}1988, the "rst Dutch National Food Consumption Survey (DNFCS) was carried out; similar surveys were conducted in 1992 and 1997}1998. In each survey, food consumption data were converted into energy and nutrients using the most up-to-date version of the Dutch food composition table. To enable valid comparisons of nutrient intake over time speci"c food composition tables (Trend Table-1 (TT-1) for DNFCS-1 and TT-2 for DNFCS-2) were created. In these tables, for 20 nutrients, the composition of 550 selected food items was compared and reasons for di!erences were investigated. The food composition table used for DNFCS-3 (last update in 1997) was the reference table. To avoid arti"cial changes, di!erences as a consequence of improvements of the database were corrected in retrospect; real changes in the food composition remained intact. In TT-1 nearly 3500 modi"cations were made. Most of them concerned the composition of macronutrients. About 40% of the corrections arose from more and better analytical data; 6% were missing values. In both TTs many changes were related to the fatty acid composition of foods and were a consequence of changing the expression of saturated, monounsaturated and polyunsaturated fat into fatty acids. In TT-2 more than 2800 modi"cations were made; besides changes in the fatty acid composition, about 20% re#ected improvements in the quality of data, and 16% were missing values. Changes in the di!erent food groups and consequences of the modi"cations are discussed in more detail.