The inactivation of Escherichia coli (E.coli) was studied in presterilized surface water sample using titanium dioxide as the photocatalyst under irradiation of BLF Fluorescent lamps. Inactivation of E.coli (10(3) CFU/mL) was achieved in 60 min in the presence of 1.0 mg TiO2/mL. Photocatalytic inactivation data was evaluated in terms of first order rate equation N/N0 = e (-kIt). The reaction rate constant k, 1.22*10(-2)(mW min/cm2)-1 was calculated.