Solid-state fermentation (SSF) is a very ancient technology employed by the eastern countries, hasattracted the attention of western countries in recent decades. Due to the engineering and environmentalaspects, solid-state fermentation has shown much promise in the development of several products andbioprocesses; however it is still in competence with the submerged fermentation (SmF) technique. Thisreview covers the definition and brief history of the SSF technique, advantages and limitations of theuse of agro-industrial residues followed by the list of recently used inert supports. A significant part ofthis review concerns some of the important factors affecting the SSF processes such as; inoculum size,incubation time and temperature, moisture content and water activity, initial pH, particle size, agitationand inoculum type. The effect of each factor on SSF processes is not only detailed theoretically but alsodiscussed via specific studies from the literature. This article will enlighten potential researchers dealingwith applied SSF processes as well as the manufacturers concerning in adding value to the agro-industrialresidues.