Recent developments in the theory of the kinetics of non-catalytic fluid-solid reactions are reviewed. Until recently, the treatments of this important group of reactions have been in an embryonic stage. In the last few years, however, significant progresses have been made in various aspects of fluid-solid reactions. In Part I, the reaction of an initially nonporous solid will be reviewed. Part II will discuss the reaction of an initially porous solid, and the reactions between two solids proceeding through gaseous intermediates will be described in Part III. Finally, the treatment of industrially important multiparticle systems will be presented in Part IV.