The Bureau of Mines investigated the adaptability of the Meteorology Research Inc. (MRI) nephelometer and the sinclair-phoenix smoke meter for use in routine, analytical, smog-chamber experiments. The sampling systems of both instruments were modified--smaller size sample input systems were studied using the nephelometer and a secondary sample system was added to the smoke meter to allow measurement of aitken or condensate nuclei. Both instruments were easily adapted for use with small smog chambers and both displayed good precision and sensitivity to aerosols. A correlation was shown to exist between the responses of both instruments to aerosol. This correlation makes it possible to report the sinclair-phoenix measurements in visibility and/or mass units if desired. Work done under an agreement with the office of air programs of the Environmental Protection Agency.