This paper presents a method to solve the periodic vehicle routing problem with service frequency. The problem consists in finding a set of paths for a crew of vehicles to deliver products or services to a set of customers in a discrete planning horizon subject to constraints as vehicle capacity, distance-time constraints, time windows, and the variable demand that implies a not defined frequency. Our method solves iteratively two mixed integer programming models. The first one assigns customers to be visited on the planning horizon. The second finds paths to visit the customers for each period. However, in case of non-feasibility a set of rules modify the allocation and the process starts again until the solution is obtained. We present an example to illustrate the method.