Enzymatic assays using CE are now among the most noteworthy applications of this analytical technique in pharmacology-related investigations. Studies of metabolic pathways of new chemical entities mediated by drug metabolizing enzymes are attracting particular attention. Conventional CE-based enzymatic in vitro assays are generally restricted to the separation of reagents after incubation performed off-line. EMMA represents an alternative and fully prospective approach, allowing injection, reaction, separation, and detection to be conducted in a single capillary. Such an on-line systemin contrast to the standard approachenables automation, miniaturization, and a significant reduction in reagent volumes, resulting in a very robust and cost-efficient method. Hence, EMMA could be a method of choice for the screening of new drugs, enzymatic inhibitors, and putative drug-drug interactions. This review provides a summary of reports covering the area of EMMA-based and related methods implemented into in vitro studies of drug metabolizing enzymes. A general description of the EMMA framework, enzyme families, and a concise discussion of the prognosis for the development of this methodology are given as well.