This paper illustrates the mechanism of gas-solid contacting in a multistage counter-current fluidized bed reactor attached with downcomers. Experimental hold-up study has been carried out extensively using the air and lime particles as gas and solid phases, respectively. The reactor was operated in continuous regime for two-phase system over a wide range of operating conditions including height of the downcomer to determine the solids hold-up at each stage of the reactor. The data was generated under steady and stable operation of the column. Based on the experimental data, empirical correlation is proposed for predicting the solids hold-up in the multistage fluidization. The results in this study assume importance from the standpoint of design and steady operation of multistage fluidized bed reactor with downcomer as an air pollution control system for control of gaseous emissions in the industries. (C) 2008 Elsevier B.V. All rights reserved.