Flow injection analysis (FIA) is well established as a powerful sample handling procedure for laboratory and process analytical chemistry, but the latter application is often hampered by the complexity of the required manifolds particularly for multicomponent analyses. In certain circumstances multicomponent process analytical chemistry is only feasible by utilising several independent FIA systems. This review presents an overview of sequential injection analysis (SIA), which addresses these limitations, and applications of the methodology to the challenging area of process analytical chemistry will be discussed. Copyright (C) 1999 Elsevier Science B.V.