A method for machining an integrally bladed rotor of a fluid-flow machine is disclosed. In accordance with an embodiment of the invention, the method includes the steps of: a) providing an integrally bladed rotor having a main rotor body and several rotor blades integrally attached to the main rotor body; b) determining the natural frequency of each rotor blade of the integrally bladed rotor; and c) machining at least one rotor blade of the integrally bladed rotor by removing material to adjust the natural frequency of the particular rotor blade to a specified value.