- The objective of this work was to determine the incidence of fungi on soybean seeds produced in Mato Grosso do Sul State, Brazil, during the 1992/93 growing seasons. Samples of 21 cultivars, from seven counties (Chapadão do Sul, Dourados, Maracaju, Ponta Porã, Rio Brilhante, São Gabriel do Oeste and Sidrolândia) were analysed, using the blotter test. Twenty-three genera of fungi were detected on the 142 samples. The most prevalent fungus, detected in 96.5% of the analysed samples, was Fusarium semitectum, followed by Aspergillus sp. (94.4%), Penicillium sp. (80.3%), Phomopsis sp. (76.8%), Cercospora kikuchii (69.0%), Cladosporium sp. (45.8%), Colletotrichum truncatum (45.1%) and Alternaria alternata (37.3%). Cercospora sojina was observed in only 5.6% of the analysed samples. The fungus that occurred with higher incidence was F. semitectum ( = 17.2%), followed by Phomopsis sp. ( = 12.2%), C. kikuchii ( = 4.4%) and C. truncatum ( = 1.8%). The results showed that the most important fungus associated with soybean seeds in Mato Grosso do Sul is F. semictectum. The storage fungi (Aspergillus sp. and Penicillium sp.) were detected at relatively high levels.