The concept of disease has been the subject ofa vast, vivid and versatile debate. Categoriessuch as ``realist'', ``nominalist'', ``ontologist'',``physiologist'', ``normativist'' and``descriptivist'' have been applied to classifydisease concepts. These categories refer tounderlying theoretical frameworks of thedebate. The objective of this review is toanalyse these frameworks. It is argued that thecategories applied in the debate refer toprofound philosophical issues, and that thecomplexity of the debate reflects thecomplexity of the concept itself: disease is acomplex concept, and does not easily lenditself to definition.