A photocatalytic microreaction system was developed and photocatalytic N-alkylation process of benzylamine, aniline, and pipelidine was examined. The reaction proceeded quite rapidly in the microreactors with immobilized Pt-free TiO2 as well as Pt-loaded TiO2, while it has been reported that the N-alkylation did not occur by the irradiation of Pt-free TiO2 in conventional batch reactors. It was revealed that by using the unique features of the continuous-flow microreactor, for instance spatial illumination homogeneity and precise control of flow and irradiation conditions, one can control the selectivity of N-alkylation and N,N-dialkylation processes. These results suggest the possibilities of a photocatalytic microreaction system on organic synthetic reactions. (C) 2007 Elsevier B.V. All rights reserved.