A framework is outlined for estimating pedestrian demand within a railway station which takes advantage of the train timetable and train frequentation data, as well as various direct or indirect indicators of demand. These may include e.g. link flow counts, measurements of density and travel times, or historical information. The problem is considered in discrete time and at the aggregate level, i.e., for groups of pedestrians associated with the same origin-destination pair and with the same departure time interval. The formulation of the framework allows for a wide applicability to various types of railway stations and input data. A preliminary case study analysis of Lausanne railway station provides an example of such an application.