Theoretical analysis has been made of evaporation of single droplets of solutions, pure liquids and their polidisperse ensembles moving in hot gas flow. The process has been considered as succession of physically different stages. Account is taken of simultaneous variation of droplet size, velocity and density of transverse vapour removal, of the structure of the intermediate solid particle, etc., and, for evaporation of ensembles of different-sized droplets, also of the difference in the dynamics of their evaporation and motion. The solutions obtained are simple analitical relations which include the existing relations for particular cases as their limiting expressions.