A method and apparatus for measuring the resistance of a winding of a converter-fed single- or three-phase machine during operation by means of a d-c measuring current. The firing instant of at least one up-commutating valve of a maching converter is delayed by a predetermined variable setting angle for generating d-c measuring currents in the phase currents, whereby the current conduction time of the up-commutating valve is shortened and the current conduction time of a valve commutating down with the valve which is commutating up with delay, is lengthened. The generated d-c measuring current is filtered out of the measured machine current and the generated interlinked d-c measuring voltage is filtered out of a measured terminal voltage of the single- or three-phase machine, and the winding resistance is determined from the linked d-c measuring voltage and the d-c measuring current by forming a quotient. Thus, it is possible to measure a winding resistance in a converter-fed three-phase machine during operation without using a nonlinear resistance circuit in a connecting lead.