Ab initio electronic structure calculations for phenol and the hydrogen-bonded complexes phenol · H2O and d-phenol · D2O were performed at the Hartree-Fock 4-31G and 6-31G** levels. Both phenol and phenol · H2O were fully structure optimized. Based on the minimumenergy structures so obtained, full normal coordinate analyses were carried out. The resulting harmonic frequencies were scaled and compared to available experimental data. The agreement is satisfactory and allows for an assignment of a majority of the bands observed in the experimental spectra. Comparison with previous calculations on (H2O)2 reveals a considerable increase in the strength of the hydrogen bond on going from (H2O)2 to phenol · H2O.