The theory of similarity of heat and mass transfer processes in bubble fluidized beds is developed. It is based on the account for a main specific feature, which distinguishes a fluidized bed from other gas-solid systems, viz, a two-phase structure of the bed: the presence of bubble and emulsion phases. The existence of these phases determined the character of transport processes in the system in many respects and imparts a number of unique properties to the system that are widely used in engineering (isothermicity, high values of the coefficients of thermal conductivity and heat transfer, etc.). A system of dimensionless governing parameters which characterize local and integral similarity of fluidized beds is found. It is shown that Fr and Ar numbers can serve as basic dimensionless characteristics of bubble and emulsion phases. The employment of these numbers makes it possible to obtain generalized relations for calculating transport characteristics of fluidized beds which are distinguished by simplicity, physical and large universal nature.