Lifetime measurements with spatial resolution of about three carrier diffusion lengths have been made in silicon high power diodes and thyristors. The method uses a pulsed 40 keV electron beam of 10μm diameter to generate excess carriers the decay of which is measured by the built‐in p‐n junction. Lifetimes larger than 0.3 μs can be measured, but may easily be extended to smaller values. An example is given of a diode exhibiting lifetime variations within a factor of four in a range of a few millimeters.