The IR spectrum of cis-1-naphthol, trans-1-naphthol, and 1-naphthol .(H2O)(n) (n = 1-3) clusters has been measured by the LR dip spectroscopy in a supersonic jet. The spectra show clear vibrational structures of the monomers and the clusters in the energy region from 3000 to 3800 cm(-1). Observed vibrational transitions are assigned to the OH stretching vibrations of l-naphthol and waters in the clusters. The size dependence of the IR bands and the cluster geometries are analyzed by using the ab initio MO method at the MP2/6-31G level. From the comparison between the observed and calculated IR spectra, we have concluded that the l-naphthol acts as the proton donor and a cyclic hydrogen-bond network is formed in the n = 2 and 3 clusters.