The role of enzyme electrophoresis is discussed as it applies to taxonomy and systematics. particularly of invertebrates. Details are given of methods for distinguishing and identifying cryptic or sibling species and the different approaches to sympatric and allopatric populations are reviewed. The calculation and uses of genetic distance measures are outlined. as are the empirical relationship of such measures to different levels of taxonomic separation. Defficulties. drawbacks and limitations of the technique are explained together with the advantages. Evidence for molecular clocks is outlined briefly and their role in systematic studies is discussed, as are methods of analysing genetic divergence data for systematic purposes. References to studies covering a wide range of invertebrate taxa are tabulated.