Rhizopus oligosporus UQM 145F was grown on cassava starch medium without a preliminary treatment of starch. The fermentation pattern of R. oligosporus is shown to be influenced significantly by the medium composition, pH of the growth culture and the size of the spore inoculum. By varying the carbon, nitrogen and mineral salt concentrations, it was found that either glucose accumulated due to excess hydrolysis of starch or single cell protein production became dominant. In the case of the carbon source, increases in the concentration of starch led to higher biomass values, but lower rates of protein production. These observations led to a new formulated medium, resulting in an 82.9% cassava starch utilization and a true protein yield of 5.32 g/100 g initial substrate. The response of R. oligosporus to inorganic compounds such as (NH4)2SO4, urea, NaCl and MgSO4 indicates an interesting fermentation control system.