Electrocoagulation is an electrochemical wastewater treatment technology that is currently experiencing both increased popularity and considerable technical improvements. There has been relatively little effort to better understand the fundamental mechanisms of the processes, particularly those that could provide design parameters to optimize the performances of this relatively simple and inexpensive technique. In a research programme to delineate the mechanisms of the fundamental processes involved in, the authors have realized that the technology has been insufficiently reviewed with emphasis on the fundamentals and their relationship to the performance of this technology. This paper presents an in-depth discussion and consideration of the factors that need to be addressed for optimum performance of this technology. Recent improvements of this technique and the theoretical model studies are also reviewed.