A guide rail (10) for the roof opening system of a motor vehicle has several lengthwise guide rail segments (12, 14) which are located in succession in the guidance direction (a), and at least one adapter (16) located in a transition area between adjacent guide rail segments (12, 14). The adapter provides for a continuous guide transition (22) between the coaxial guideways (18, 20) of the adjacent guide rail segments (12, 14). In such a guide rail, viewed over the length of the guide rail, guideways and cable channels can also be arranged nonuniformly and the guide rail segments can be made completely individually, especially optimized for the respective area of the task.