In this chapter, I expose the main properties and theoretical background of a somewhat out-of-fashion technique, multilocus enzyme electrophoresis (MLEE). I show that the remarkable properties of this marker—clear Mendelian inheritance, codominance, strong phylogenetic signal—are still valid, although of course more modern markers now are able to yield far more refined results. MLEE can still be used in many circumstances when a cheap and reliable marker is required. I summarize what have been the main contributions of MLEE to the study of parasites and other pathogens.
