Abstract: Trichoderma reesei QM9414 was co-cultured with Aspergillus terreus SUK-1 for cellulase and reducing sugar production on sugar cane bagasse in solid substrate fermentation. The highest cellulase activity (FPase 0.68 (IU/ml), β-glucosidase activity (0.08 IU/ml) and reducing sugar concentration (1.4 mg/ml) were obtained in mixed cultures using inoculum ratio of 2:1 (Trichoderma : Aspergillus) compared to other ratios investigated (1:2 and 1:1). Nevertheless, experiments with pure culture of T. reesei was found to be better in terms of the production of FPase (1.4 IU/ml) and reducing sugar concentration (2.3 mg/ml), The addition of A. terreus to T. reesei in cultures of 2:1 inoculum ratio increases the production of β-glucosidase (the highest activity of 0.08 lUlml was detected in cultures of 2:1 ratio as well as in pure cultures of A. terreus). Nevertheless, this enhanced (β-glucosidase activity in mix culture could not result in enhanced substrate utilization and reducing sugar production. It was found that the highest percentage of degradation (25%) was achieved when pure cultures of T. reesei was employed followed by when pure cultures of A. terreus was employed (22%) and when mix cultures of 2:1 inoculum ratio was employed (22%). This suggests that synergism of β-glucosidase and cellulase to enhance substrate degradation was better affected using pure culture than mixed culture in solid substrate fermentation of sugar cane bagasse.