Particulate matter including PM10, PM2.5, and PM1 are one of the major concerns in the atmospheric environment. Due to the simplicity of their construction and use, and their relatively sharp cutoff characteristics, cascade impactors have been widely used for the size classification of particulate matter. In this study, a 5-stage cascade impactor (K-JIST cascade impactor) was designed and tested. Each stage of the impactor was calibrated using a gravimetric or counting method and the fully assembled impactor was evaluated by using a fluorometric method. Experimental data were fitted by non-linear regression using a newly suggested sigmoidal function, and stage response functions were obtained from the collection efficiency curves. Calibrated cut-point diameters were well matched with designed values with sufficient stiffness. Total wall losses, inlet sampling efficiency and the distribution of wall losses for each impactor stage were also evaluated. (C) 2003 Elsevier Science Ltd. All rights reserved.