Dose distributions were evaluated under thin sheet lead used as surface bolus for 4‐ and 10‐MV photons and 6‐ and 9‐MeV electrons using a parallel‐plate ion chamber and film. A narrow, significantly low dose region (−17%) was noted for 4‐MV photons, whereas a 6% increase in dose was present for 10‐MV photons. The dose was elevated 15%–22% near the surface of electron fields with lead bolus, but depth dose relationships were similar to soft‐tissue‐equivalent (STE) bolus. Investigation of partial‐field bolus (2‐cm‐diam circle) documented reduced doses due to lack of lateral electron equilibrium for 10‐MV photons, which was less evident using lead, and large edge effects (up to 30%) for electrons using either lead or STE bolus. Dose distributions on sloped surfaces with electron fields were similar for lead and STE; both require thickness adjustment to achieve a desired effective thickness normal to the surface. Lead bolus has been used successfully in clinical practice for photons.