The FlexRay communication protocol is expected to be the de facto standard for high-speed, in-vehicle communication. In this paper, we formally investigate the scheduling problem for the dynamic segment (DS) of FlexRay. We take the bounds on the generation times and the timing requirements of the signals into consideration to propose a reservation-based scheduling approach that preserves the flexible medium access of the DS. To obtain efficient schedules, we formulate a nonlinear integer program- ming problem (NIP) that minimizes the required duration of the DS. This NIP is then decomposed into two linear binary integer programming problems to facilitate the computation of feasible message schedules. An experimental study illustrates our message scheduling approach for the DS of FlexRay.