Among the 26,000 isolates of filamentous and yeast-like fungi stored at the Mycothèque de l'Université catholique de Louvain (MUCL), approximately 300 isolates were identified as Fusarium. These isolates originated from various countries worldwide and were obtained from different vegetal host species, from soils or from stocks of animal or human foods. The research work undertaken on that genus at MUCL is based on three different approaches : taxonomic studies within the genus, detection and biochemical characterization of mycotoxins (more particularly fumonisins), and analysis of their biosynthetic pathways. The taxonomic approach, which is our research topics, is based on the implementation of the morphological identifications by theuse of molecular biology tools. For this purpose, ribosomal DNA, mitochondrial DNA and several genes allowing the distinction between Fusarium species (b-tubulin, calmodulin, elongation factor) are analysed. DNA is amplified by the polymerase chain reaction (PCR) technique, using rDNA and mtDNA specific primers, or primers constructed from genes sequences already published. After sequencing, aligned sequences are analysed together with those of Fusarium spp. available in the EMBL databank. Phylogenetic relationships between MUCL and references isolates are then analysed using PHYLIP software. Integration of morphological and sequence-defined groups will help to clarify the taxonomic position of the isolates within the genus Fusarium, and to develop rapid identifcation tools for further research and commercial services encountered in the MUCL collection. Furthermore, in the frame of the increasing importance of this mycotoxinogenic fungus in human and animal health, overlapping of the taxonomic data with those obtained for the mycotoxins analyses will serve to the construction of a database which will help to develop adequate strategies of management of mycotoxin contamination.