Two strains of fungi, one belonging to the genus Aspergillus and the other to the genus Rhizopus, were grown on cassava media in a moist-solids fermentation process. Growth characteristics and toxicity were assessed by observing the effects of the fermented products on day-old ducklings. Feed intake, conversion efficiency and organ weights were recorded. The control diet gave considerably better results in conversion efficiency and weight gain than the fermented products; feed consumption was highest in the diet constituting the unfermented cassava. No mortality was recorded over an eight-week feeding period. Histopathological examination of livers and kidneys showed no abnormal findings, thus indicating that the fermented products were free of toxic metabolites and suitable for consumption.