The composition and abundance of megabenthic fauna caught by the commercial trawl fleet in the Alboran Sea were studied. A total of 28 hauls were carried out at depths ranging from 50 to 640 m. As a result of a hierarchical classification analysis four assemblages were detected: (1) the outer shelf group (50-150 m), characterised by Octopus vulgaris and Cepola macrophthalma; (2) the upper slope group (151-350 m), characterised by Micromesistius poutassou, with Plesionika heterocarpus and Parapenaeus longirostris as secondary species; (3) the middle slope group (351-640 m), characterised by M. poutassou, Nephrops norvegicus and Caelorhincus caelorhincus, and (4) the small seamount Seco de los Olivos (310-360 m), characterised by M. poutassou, Helicolenus dactylopterus and Gadiculus argenteus, together with Chlorophthalmus agassizi, Stichopus regalis and Palinurus mauritanicus. The results also revealed significantly higher abundances in the Seco de los Olivos seamount, probably related to a higher food availability caused by strong localised currents and upwellings that enhanced primary production. Although depth proved to be the main structuring factor, others such as sediment type and food availability also appeared to be important. Differences between shelf and slope assemblages could be in part related to a greater dependence on benthic resources in the former and a higher use of planktonic resources in the latter.