A total of 399 indigenous Fusarium strains mainly isolated from silage maize were tested for the production of zearalenone and type A trichothecenes by thin-layer chromatography and biological assays. About 45% of the isolates examined were capable of producing different levels of zearalenone and trichothecene toxins on a cracked corn substrate. The majority of these strains (75%) produced zearalenone only and no trichothecenes type A. The results of the biological tests indicated a higher rate of toxin-positive extracts than chemical analysis. Isolates of nine out of seventeen Fusarium species examined produced one or several mycotoxins looked for. The most important toxin producers were F. culmorum and F. crookwellense (zearalenone) and F. sporotrichioides (trichothecenes type A), respectively. F. avenaceum, the species most frequently isolated from silage maize, produced neither zearalenone nor trichothecenes but avenacein Y a antibiotic compound. First results of a study of the production of type B trichothecenes have shown that indigenous F. culmorum isolates were capable of producing high levels of deoxynivalenol.