Abstract. Artificial reefs in marine environments are in most cases submerged structures consisting of dumped waste material or specific constructions made with the purpose of enriching the local fish populations and other marine life to the benefit of recreational and commercial fisheries. Such structures are susceptible to fouling and will successively develop assemblages, which may or may not resemble epibioses on natural substrata. Studies of artificial reefs have focused predominantly on fish assemblages and have largely disregarded the development of sessile biota and their structural and functional relationships. In addition, most studies are from tropical or subtropical environments. To manage and understand artificial reefs, a whole-ecosystem approach is necessary, incorporating studies of all aspects of hard substratum ecology including both structural and functional variables. This review is an attempt to evaluate the present knowledge of ecological aspects of artificial reefs, emphasising the role of sessile hard substratum biota.