More than 600Fusarium strains were screened for their ability to produce moniliformin in vitro. They represented 90 species and 15 sections (without sectionPseudomicrocera). A simple TLC-method (agar plug method) was tested for its applicability to detect moniliformin in fungal cultures. It revealed moniliformin production in 146 strains representing 32 species, all belonging to sections of which the teleomorph is known to beGibberella. The results by and large agree with earlier published data. However, some species did not show any moniliformin production in contrast to other reports. Furthermore, moniliformin production is reported for the first time in two known and in two not yet described species. 58 species were unable to generate the toxin. The results support the importance to include mycotoxin production of fungi as a criterion in a polyphasic taxonomy.