This research was undertaken to investigate the impact performance of longitudinal barriers when placed on sloping terrain. Tasks performed included (a) a determination of typical conditions for which longitudinal barriers are placed on sloping terrain,(b) an evaluation of the impact behavior of widely used barrier systems when placed on sloping terrain, and (c) the development of guidelines for selection and placement of barriers on sloping terrain. Crash tests and the HVOSM computer program were used to evaluate impact behavior and to develop guidelines. Factors considered in the guidelines include roadway and shoulder cross slope, cut and fill slope, barrier offset, and barrier type. It was found that W-beam and Thrie-beam barriers are more sensitive to the effects of sloping terrain than are cable barriers.