The total transmitted energy loss distribution of an initially monoenergetic electron beam was measured for thin films of varying atomic number. The films were thin enough (100 to 1500 A) and the incident electrons energetic enough (5 to 20 kev) so that the scattering distributions observed were representative of single and plural scattering. The distribution of energy losses above 100 ev for the organic films appeared consistent with a W-2 dependence, where W is the energy lost by the electron. From the experimental energy loss distributions measured, a value for the average energy loss per inelastic event, [image], for Formvar (C5H8O2), polystyrene (C8H8), and carbon was found of approximately 60 [plus or minus] 10 ev. For the other films investigated[long dash]Al2O3, aluminum, copper, gold, and silver[long dash][image] was found to increase with the mean atomic number of the target materiaL.