IR spectra of trans-1-naphthol-(H2O)(n) (n = 0-3) clusters in the S-1 state were measured by UV-IR fluorescence dip spectroscopy. The observed dip spectra were compared with theoretical ones of various stable conformations predicted by ab initio MO calculations. From the comparison, linear (n = 1) and cyclic hydrogen-bond structures (n = 2 and 3) were concluded. The relation between the structures and photochemical reactivity was discussed. (C) 2012 Elsevier B.V. All rights reserved.