Nanoporous TiO2 membranes (1 cm in diameter, 9 cm in length) were prepared by coating colloidal TiO2 sol solutions on the outer surface of cylindrical porous membranes (average pore diameter I um) and firing at 450° C, and applied in a photocatalytic membrane reactor. In this system, a feed stream is forced through the membrane to yield a purified permeate where organic pollutants are degraded by photocatalytic reaction. Methylene blue (MB) was used as a model solute and was irradiated with blacklight lamps (BL) to promote the photocatalytic reaction. TiO2 membranes with an average pore diameter of 10nm, yielded a normalized permeate concentration relative to feed concentration, C-p/C-f, of approximately 40% (60% rejection), based on the molecular sieving effect without BL irradiation. The normalized permeate concentration of MB decreased to 5% under BL irradiation, depending on experimental conditions such as feed concentration and applied pressure. The molecular sieving and the photocatalytic reaction can be combined to improve the selectivity. Permeate volume flux without BL irradiation decreased with an increase in feed concentration of MB, because of pore blocking by MB. On the other hand, the permeate flux increased with BL irradiation and showed approximately constant values irrespective of MB concentration. This suggested that the permeate flux was restored by photocatalytic degradation of MB which fouled the membranes.