Rice chaff was used as the substrate for the production of fibrinolytic enzyme by Fusarium oxysporum in solid state fermentation. The optimized moisture content of the medium was 30 - 50% (v/w). An inoculum of 5 - 10% (v/v) and an average particle size of 400 mu m for the substrate were optimum for productivity and enzyme activity of 80 IU per mi filtrate was achieved after 96 hours of fermentation.