Recent elimination of the Interstate Commerce Commission, pending rail mergers of major carriers, and the recent attempts to set maximum reasonable rate guidelines have indicated the concerns of captive shippers over rates and service. This study has shed some light on the grain marketing practices ofN.D. grain elevators and has explained and measured the competitive factors influencing rates, including their role in market dominance determination. The study shows that carriers' rates are constrained by four factors not under the control of the carrier. These factors include intramodal competition, intermodal competition, geographic competition, and product competition. While the concepts of intermodal competition and intramodal competition have been widely accepted by many, this is not necessarily the case for geographic and product competition. Regions which grow relatively unique crops such as the Upper Great Plains and the Pacific Southwest have higher rail rates as carriers are not constrained by geographic competition in those areas. In addition, shipments of durum and other crops which don't have many substitutes have higher rates as carriers don't realize product competition for these movements. Finally, the study highlights the importance of efficient and effective rail service for the future ofN.D. agriculture. The explanations of current N.D. grain marketing practices and of the factors influencing rail rates should allow for more enlightened decisions regarding policies that may affect the future ofN.D. rail service.