The use of a solid-phase reactor coupled on-line to a flow injection manifold can significantly expand the potential of flow injection analysis by enhancing such basic analytical parameters as sensitivity and selectivity, and allowing implementation of specific reactions. Typically, solid reactors involve chemical reactions (whether enzymatic, immunoassay, ion-exchange or redox) or act as sorbent extractants or reagent releasers. These aspects and major trends in their use in conjunction with flow injection manifolds are examined here.