The incidence of human infections by Fusarium is increasing in contemporary medicine. Since the recognition of the species involved in such processes is generally difficult for non-specialists, we include here the main criteria that should be used in the identification of the responsible species. The most frequent species are F. verticillioides, F. oxysporum and F. solani, which are illustrated. The differences between Fusarium and Acremonium and Cylindrocarpon, two close genera, are discussed. The latter two are also illustrated. The main morphological characteristics of Fusarium such as sporodochium, conidiophore, conidiogenous cell, phialide, locus, macroconidia, mesoconidia, microconidia and chlamydospores are defined and illustrated. A key to the identification of Fusarium species isolated from human lesions is also included.