The ability of a strain of Alternaria tenuissima Kunze (IMI 301005) Wiltshire to degrade and alter the nutrient profile of three common Nigerian cereals was studied. The grains involved were Pennisetum glaucum, Sorghum vulgare and Oryza sativa. Fat, fibre and protein decreased in the inoculated substrates, and this was accompanied by an increase in ash content. The highest levels of cereal degradation by the mould were attained at pH 6.8 and at temperature range of 30-35 °C. Within 48 hours of incubation, extracellular proteases were detected in all the culture media.