Presented in 5 th EURO/INFORMS Joint International Meeting, July 6-10 2003 İstanbul, Turkey Integer Linear Programming Formulation of the Generalized Vehicle Routing Problem Imdat Kara, Tolga Bektas Baskent University, Dept. of Industrial Engineering, Baglica Kampusu, Eskisehir Yolu 20. km., Ankara, Turkey Abstract The Generalized Vehicle Routing Problem (GVRP) is an extension of the Vehicle Routing Problem (VRP) defined on a graph in which the nodes (customers, vertices) are grouped into a given number of mutually exclusive and exhaustive clusters (nodesets). In this paper, an integer linear programming formulation of the GVRP with O(n 2 ) binary variables and O(n 2 ) constraints is presented. It is shown that, under specific circumstances, the proposed model reduces to the well-known routing problems. The computational performance of the models solved using a commercial code on test problems are also presented. Key words: Vehicle Routing Problem, Integer Programming, Traveling Salesman Problem