This paper presents a review of part of the work done on photocatalytic reactors. Being aware of the comprehensive reports already existing on the chemistry of these reactions [A.M. Braun, L. Jakob, E. Oliveros, C.A. Oller do Nascimento, Adv. Photochem. 18(1993) 235; O. Legrini, E. Oliveros, A.M. Braun, Chem. Rev. 93 (1993) 671; D. Bahnemann, J. Cunningham, M.A. Fox, E. Pelizzetti, P. Pichat, N. Serpone, in: G.R. Helz, R.G. Zepp, D.G. Crosby (Eds.), Aquatic and Surface Photochemistry, Lewis Publishers, Boca Raton, FL, 1994, p. 261; M.R. Hoffmann, S.T. Martin, W. Choi, D.W. Bahnemann, Chem. Rev. 95 (1995) 69; D. Bahnemann, in: P. Boule (Ed.), The Handbook of Environmental Chemistry, Part I, Vol. 2, Environmental Photochemistry, Springer, Berlin, 1999, p. 285] we have focused our work on two main themes: (i) light absorption evaluation when artificial light is used and (ii) description of reactor configurations and applications when solar radiation is employed. A classification is proposed for both topics and typical examples have been chosen to illustrate the specified concepts. (C) 2000 Elsevier Science B.V. All rights reserved.