The eruption of Mt Pinatubo (15.14 degrees N, 120.35 degrees E) in the Philippines on 15 June 1991 produced the largest volcanic effluents into the stratosphere as observed by satellite measurements. In this paper we demonstrate the application of an inversion technique to satellite observations to infer the stratospheric aerosol size distributions before and after the eruption. The U.S.A. NASA SAGE (Stratospheric Aerosol and Gas Experiment) II satellite data were used. As a result, the stratospheric aerosol size distributions were found to be bimodal due to the addition of larger particles from Mt Pinatubo ejection. In addition, aerosol parameters such as extinction coefficient, effective radius, total surface area, and mass loading were used to track the northward and southward dispersion of Pinatubo volcanic plume unmistakably. For example, by 18 July 1991, the Pinatubo plume had reached as high as 22 km in the stratosphere above Taiwan area. The extinction profiles for September and October 1991 cases were enhanced about two orders in magnitude at the altitude of 20-24 km owing to Pinatubo aerosols. Regarding the transport in the southern hemisphere, for five months after eruption, the plume had reached the Antarctic stratosphere, and dispersed vertically as high as 40 km. In middle Antarctic stratosphere, the aerosol extinctions were increased in general by an order of 10(3)-10(5) due to the intrusion of Pinatubo plume. The second mode at 0.5 mu m was found compared with the one at less than 0.1 mu m, generally found in background stratosphere.