An optical fibre reactor with 30 hexagonal-shaped channels distributed within the optical fibre structure was investigated as a gas-phase photocatalytic reactor. TiO2 photocatalyst, with SiO2 sol acting as a binder, was coated on the channel walls at a thickness of 1.5 mu m. Effective light propagation lengths of 3.4 and 4.9 cm were observed for incidental angles of 81.5 degrees and 87.1 degrees, respectively. The TiO2-coated channelled optical fibre reactor (COFR) was assessed for the photocatalytic degradation of gas-phase ethylene. The photocatalytic reaction rate of ethylene degradation was linear with respect to the incident photons. The reaction rate order for the incident photons was determined to be 0.93. Despite a longer effective light propagation length for an incidental angle of 87.1 degrees, the quantum yield was independent of the incidental angle. The independence of the quantum yield on the incident photons and the angle of light incidence was attributed to the COFR design, where the propagating light was wholly confined within the reactor and, in turn, more effectively utilised by the TiO2. (C) 2009 Elsevier Ltd. All rights reserved.