Correction factors for the effect of thickness on the selfscattering, self-absorption, and backscattering of beta particles from indium foils were determined for irradiated foils of 0.03 to 100 mg/cm2. The data were corrected for the activity produced by epithermal neutrons, self-shielding of thermal neutrons by the foil during irradiation, the backscatter from the foil support, and the contributions of gamma and x rays to the counting rate. The multiple beta spectra of indium produced a minimum in the self-absorption and self-scattering correction curve in the GM detector at approximately 1 mg/cm/ sup 2/ and a maximum at approximately 12 mg/cm2. The selfabsorption curve for indium in the 2 pi counter has the expected shape for a beta emitter with multiple spectra. The self-scattering and self-absorption correction factors for a 100 mg/cm2 indium foil are approximately 1.5 for a GM detector at 7% geometry and approximately 3 for a 2 pi counter. (D.L.C.).