A radon-aerosol chamber having an inner volume of approximately 25 m(3) has been developed at the National Institute of Radiological Sciences (NIRS). The chamber is designed to control temperature, relative humidity, aerosol concentration, radon concentration, and pressure differentials between inside and outside the chamber. We evaluated its performance as an aerosol chamber. Temperature and relative humidity can be controlled from 278 to 303 K, and 30% to 90%, respectively, and pressure differentials between inside and outside the chamber can be maintained at negative values. Temperature and relative humidity fluctuations are very small. The concentration of particles inside the chamber can be controlled from 10(8) to 10(10) m(-3). Particle concentrations and distributions are very stable. The particle concentration fluctuation is within the statistical error of the TSI CPC3010 particle counter. Changes in temperature and relative humidity had little effect on particle concentrations and their distributions. (C) 2003 Elsevier Ltd. All rights reserved.