The book has applied DEA model to measure scale efficiency of food firms in Vietnam from 2004 to 2008. The purpose of this book is to measure scale efficiency, so analyzing scale efficiency is strongly focused. The result from DEA method is interpreted as follows. The number of businesses operating at optimal scale is 15, 33, 36, 9, and 13 for each year from 2004 to 2008. Simply, the numbers of businesses operating at increasing returns to scale are 877, 923, 913, 859, and 830. In addition, a small part operates with decreasing returns to scale. After measuring the scale efficiency of these firms, authors use Tobit model to find the factor that affect firms operation. The result from this model shows that wage-labor ratio and D1 (Northern) had a positive effect on operation efficiency of food firms.