The stator cores of large electrical machines are supported in a steel frame in which electrical currents are circulated by leakage flux from the core. These currents can cause serious overheating. The paper gives a qualitative review of the electromagnetic factors which affect the flowof these frame currents. The work shows that the effects of frame currents may be reduced if the frame members are connected electrically in a way which more effectively suppresses core-end leakage flux.