Abstract: A guide roller assembly is disclosed for use with vertically moving members such as in offshore drilling rigs. The assembly preferably includes a pair of guide rollers which are supported on a cylindrical, rotational mounting shaft, with a biasing means applying a torque to the shaft in order to maintain the guide rollers adjacent respective guide surfaces. An adjustment subassembly is provided to vary the position of the guide rollers with respect to the guide surfaces. This subassembly includes a tubular support which has an elongated circular opening receiving the cylindrical mounting shaft and which is mounted in a circular bore. The circular opening of the support is eccentric with respect to the circular bore, such that rotation of the support adjusts the position of the shaft and rollers.