Heat and mass transfer phenomena are found everywhere in nature. They are of importance in almost all branches of Science and Technology for their varied practical involvement. Some of the fields wherein heat and mass transfer flows are significant are Power Engineering, Civil Engineering, Chemical Engineering, Aeronautics, Refrigeration and Air conditioning, Environmental Engineering, Biological, Metallurgical and Industrial processes. The aim of the present dissertation is to study the radiation effects on unsteady heat and mass transfer flow of a chemically reacting fluid. Chapter – I deals with the radiation effects on unsteady heat and mass transfer flow of a chemically reacting fluid past a semi-infinite vertical plate with viscous dissipation. Chapter – II deals with the radiation effects on unsteady heat and mass transfer flow of a chemically reacting fluid past an impulsively started vertical plate.