Maize Grain Samples Were Collected from stores and markets in Shashemene and Alemaya regions. Samples were rated asrndamaged, Hornlal and malted. Nannal and damaged samples were rated based on percentage of kernel discolouration,rnwrinkledness, floating ofke~le1s in water and attack by insects.rnMycofloral study of the three sets of samples showed that the three tox.jgenic fungal genera: Fusarium, Aspergillus andrnPenicillium were COllunon in maize in Ethiopia. Among these toxigenic fungi Fusarium was the most common genus,rncomprising 17.5 % of the total fungi isolated and was recovered from 80.5 % of the samples investigated,rnSpecies of fusarium were most prevalent in damaged and malted samples than in nonnal samples. TIle ftmgus wasrnrepresented in 91.7 % and 28 % of the total fungal isolates in damaged and malted samples respectively. In the normalrnsamples, however, Aspergillus and Penicillium spp were more prevalent and they were represented in all the samplesrnexamined.rnPreliminary test result of screening toxigenic fusarium isolates using the brine shrimp (Artemia salina) bioassay showed thatrn93 % of them were tmdgenic. The frequently occurring toxigenic fusarium were identified to be Fusarium prolijeratum,rnFusarium gramil1earum, Fusarium subglutillGns and Fusarium alllhophilum.rnIsolates of these frequent toxigenic species were grown on sterile shredded maize grain and their extracts were assayed forrntoxicity on the brine shrimp larvae. The results indicate production of methanol and/or chloroform soluble toxic metabolites.rnBioassay directed isolation of toxic principles from chloroform extract of F. graminearum isolates showed production ofrnzearalenonc and trichothecene compounds (TA and TB). Based on their physicoÂ· chemical data four compOlUlds that belongrnto the fumonisins were isolated from methanol extracts of F. proliferatum isolates.rnTIle results of the study on screening of toxigenic fusarium and bioassay directed isolatfon and purification of toxicrnprinciples indicated the importance of brine sluimp bioassay in screeuing toxigenic fusarium and detection of fusariumrntoxins.rnToxicity assay results from extracts of selected grain samples of the three sets of samples indicated that 93 % of the testedrnsample extracts were toxic. In the natural occurrence study of the toxins, zearatenone and the trichothecenes (TA and TB)rnwere detected in 50, 50, and 75 % of the damaged samples examined respectively. The estimated concentration ranges fromrn0-0.42 J.tglg for zearalenone, 0-1.5 J.tglg for TA and 0Â·2.3 J.tglg for TB. The fumonisins, on the other hand, were detected inrnall the samples examined with the highest concentrations in the malted and damaged samples.rnThe results of this study showed that toxigenic fusarium are associated with maize samples and their toxins are fOlmd on therngrain. TIle biological effect and thermostability of some of the toxins indicates the health hazard of consuming mouldrninfected grains, particularly damaged and malted grains. This necessitates the quality control of maize grain destined for human consumption.