Absorbed dose and energy distribution of scattered photons that contaminate high-energy photon beams were calculated for 6-MV and 21-MV sources using the Monte Carlo method. The percentage of the absorbed dose at the central axis is < 3%. The main sources of scattered photons are the primary collimator for 6-MV and the flattening filter for 21-MV sources, respectively. The absorbed dose from the phantom scattered photons was calculated by a semi-empirical method. The dominating contribution to the absorbed dose outside the primary beam is due to these phantom scattered photons. In the surface region of the phantom, electrons from the air and collimators may give rise to a high absorbed dose.