A technique has been developed to measure the effective backscatter coefficient in resist that is more reliable than conventional techniques since (1) it does not require precise information about the form of the backscatter profile, and (2) it makes use of the complete resist exposure response function. The estimated backscatter coefficient on Si for 100 keV electrons has been found to be 0.38+/-0.05, significantly lower than other published values determined at this energy. Within the accuracy of the measurement, the backscatter coefficient is the same for tests determined by scattering with angular limitation projection electron lithography and direct write exposures.