An aerosol test chamber was described which can be used to evaluate and calibrate several aerosol measuring instruments and samplers simultaneously. The chamber has a hexagonal cross section, a height of 2.4 meters and an effective diameter of 1.2 meters. The aerosol plus diluting air is introduced at the top of the chamber, where it is mixed by the energy of the aerosol jet. The floor of the test station is a 1.16 meter diameter turntable under which there are outlet valves for the unsampled aerosol and inlets for vacuum and electric connections. It normally takes from 10 to 30 minutes to reach a stable particle concentration in the chamber at aerosol inlet flow rates of 300 and 80 liters per minute, respectively. The chamber was evaluated using monodisperse liquid particles in the size range 2.5 to 15 microns, and polydisperse coal dust and Arizona road dust consisting of particles up to 20 microns in diameter. Determinations of particle concentration in the test chamber, with respect to spatial uniformity and temporal stability, were made. At input aerosol flow rates of between 80 and 300 liters per minute, uniform concentrations of both monodisperse liquid particles and polydisperse particles were observed, and concentrations remained stable over a period of 1.5 hours.