The lateral mixing of coarse particles (lignite, d(p)=6-13 mm) was studied in three rectangular fluidized beds, 0.3 m, 0.4 m and 0.5 m in length and 0.1 m in width, connected respectively with a fine particle (silica gel, d(s)=0.2186 mm) circulating bed (ID 0.115 m, height 3.2 m) crossflowing the rectangular beds. Residence time distribution and dispersion coefficients of the coarse particles along the lateral direction were experimentally investigated. The results demonstrated that this lateral flow could be described by the one-dimensional dispersion model. Dispersion coefficients in the range of 3x10(-4)-16 x 10(-4) m(2) s(-1) were obtained. It was concluded that the mean residence time decreased with increasing circulating rate of the fine particles to some extent and increased with increasing gas velocity and coarse particle size. The Peclet numbers (U(p)L/D-p) were in the range of 5-10.