The supersonically cooled hydrogen-bonded phenol.oxirane complex was studied using mass- and isomer-selective laser spectroscopic techniques. The S-1<--S-0 vibronic spectrum was measured by mass-selective two-color resonant two-photon ionization. UV/UV-hole-burning experiments prove that the whole observed spectrum is due to only one isomer. High-resolution fluorescence emission spectra yielded five different intermolecular S-0 state vibrational fundamentals as 15, 27, 39, 83, and 177 cm(-1), which are assigned as the rho(1)", beta(1)", tau ", beta(2)", and sigma " modes, respectively, based on ab initio calculations. The analogous S-1 state intermolecular vibrations were also assigned, based on frequency and Franck-Condon activity. The observation of the rho(1) and tau intermolecular vibrational transitions in both excitation and emission implies that phenol.oxirane is asymmetric (chiral), even though the H-donor is C-s sand the acceptor C-2v symmetric. Four different ab initio structure optimizations and normal-mode calculations were made, to compare the performance of the self-consistent field (SCF) and Becke-Lee-Yang-Parr (B-LYP) density functional methods, using the 6-31G(d,p) and 6-311+ + G(d,p) basis sets. The SCF/6-31G(d,p) method and the B-LYP method with both basis sets indeed predict chiral minimum-energy structures. The B-LYP/6-311+ +G(d,p)and SCF/6-31G(d,p) normal mode frequencies agree well with the experimental S-0 state frequencies, with rms deviations of 4%. The MP2/6-31G(d,p) hydrogen bond well depth is D-e = 6.9 kcal/mol and the dissociation energy is D-0 = 5.7 kcal/mol.