In dose calculations for external beams, Batho's correction factor applies to internal heterogeneities that cover the entire cross section of the beam. This study examines the possibility of combining Batho's correction factor with a scatter summation method, akin to that of Day, for heterogeneities that cover only part of the beam and for arbitrarily located points. The results of such calculations for beams of60Coγ photons are compared to Monte Carlo calculations by Webb and Fox and experimental data by Sontag. It is concluded that the technique, with some exceptions, yields results that are superior to the simple Batho correction factor.