Abstract: A guide rail system for guiding an elevator car or a counterweight in an elevator shaft includes a pair of .OMEGA.-shaped guide rails (1, 2) having adjacent ends connected by a connecting element. The guide rails (1, 2) have a hollow cylinder-shaped rail body (3) with a pair of flat ends (4, 5). The connecting element includes a tube-shaped connecting member (6) inserted into the rail bodies and a base plate (7, 7a, 7b, 7c) placed under the free ends (4, 5) and attached thereto by fasteners (12). A wedge body (10, 10a, 10b) on the base plate (7, 7a, 7b, 7c) extends into an opening (11, 15) formed in the connecting member (6) to expand the connecting member into locking engagement with the guide rails (1, 2).