A technique for the simultaneous quantitative analysis of carbon, nitrogen, and sulfur using in-beam gamma-ray spectrometry has been developed for use with atmospheric aerosol samples. Samples are collected on quartz filters, and the aerosol composition is determined by analyzing the gamma-rays emitted following the inelastic scattering of 7.3-MeV protons. Samples are nondestructively irradiated for 1000 s in a helium atmosphere, are not subjected to reduced pressures, and can be used for subsequent analysis. Detection limits for atmospheric sampls are in the microgram per sq cm range with a precision of 5%. The technique is compared with several more conventional methods of analysis. (Copyright (c) 1978 by the American Chemical Society.)