The structures, hydrogen bonding, intramolecular proton transfer processes, and vibrational frequencies of 2-(2’-hydroxyphenyl)benzoxazole in the ground state and the first excited singlet state were investigated by ab initio calculations (mainly at the SCF and CIS 3-21G* levels, but with supplementary calculations at the SCF/6-31G*, MP2/3-21G*, and MP3/3-21G* levels). Analysis of intramolecular proton transfer included plots of energy, O ... N distance, and O ... H distance as functions of the internal reaction coordinate. The results confirm that the most stable forms are the (O-H .... N)-bonded enol form in the ground state and the (O ... H-N)-bonded keto form in the first excited singlest state and suggest an in-plane mechanism for the excited state proton transfer which is powered by the O-H stretching vibration once the O and N atoms have been brought into proximity by in-plane bending.