A method for installing a guide rail of an elevator installation arranged in an elevator shaft, wherein the guide rail includes a multiplicity of guide-rail segments that are aligned and arranged in a row one beside the other, includes the following steps: fixing an aligning element in the elevator shaft at a first point in relation to an aligned and fastened first one of the guide-rail segments, wherein the first point is positioned on a route provided by horizontally directed parallel displacement of the route formed by the first guide-rail segment; fixing the aligning element at a second point, in the form of a reference point, in the elevator shaft, an aligning-element portion for aligning a second one of the guide-rail segments therefore being formed between the first and the second points; and aligning the second guide-rail segment relative to the aligning-element portion.