The major aim of this work is, to help clarify the interrelationships of catfishes, with major implications on the study of the general evolution of these fishes. A great part of this work, therefore, deals with a cladistic analysis of catfish higher-level phylogeny based on extensive morphological data, in which are included some terminal taxa not included in previous analyses, but principally a large number of characters traditionally excluded from those analyses, with particular attention being given to catfish morphology. This analysis gives particular importance to complex, integrated structures. It will be interest to students, ichthyologists and biologists working in evolution, taxonomy and phylogeny.