In the presented paper preliminary results of glucose oxidation on illuminated titania are reported. For comparison, results of direct glucose photolysis are also included. At high glucose concentration, up to 1.4 g/dm3, the yield of 3 hour reaction, determined by COD measurements, was small and amounted to about 5.8%. Additionally, pH measurements show, that oxidation of glucose leads to formation of acidic compounds – after 3 hours the pH lowered from 6.5-6.8, depending on glucose concentration, to about 4.5. Attempt has been undertaken to identify some of the intermediates of the photocatalytic reaction using GC-MS analysis of specially treated samples of the reactor slurry. The analysis showed the existence of intermediates which were formed both as a result of intramolecular changes and of oxidation reactions. Five acidic derivatives were found among the intermediate compounds.