Gas phase Raman scattering spectroscopy is being used as a new tool to study chemical processes taking place at high temperatures in chemical vapor deposition (CVD) systems. This technique allows measurement of changes in species concentration as well as gas temperature with spatial resolution of 0.1-0.5 mm without perturbing the CVD system. Studies of the decomposition of NH3 and SiH4 in a typical CVD system are presented as an example of the application of this technique. Measurements of NH3 concentration profiles, both normal and parallel to an rf-heated susceptor in H2-N2 gas mixtures, are presented. Attempts to measure SiH4 concentration profiles were thwarted by fluorescence from a trace impurity in the same spectral region. © 1976, The Electrochemical Society, Inc. All rights reserved.