The molecular structure, linear and nonlinear optical properties, and electronic properties of 4,5-diphenyl-2-2-oxazole propionic acid (oxaprozin) as a monomer were investigated by using Hartree-Fock (HF) and density functional theory (DFT) calculations that used 6-31G(d,p) basis set. The first-order hyperpolarizability of oxaprozin (OXA) was found to be 1.117 x 10(-30) esu. The structure of oxaprozin dimer with HF/6-31G(d) level caused by the shifts of O-H and C=O bands in the vibrational spectra of oxaprozin were also studied. Moreover, these calculated frequencies of oxaprozin dimer were compared with the solid FT-IR and FT-Raman spectra. The theoretical frequencies and infrared intensities were showed a good agreement with experimental data. (C) 2010 Elsevier B.V. All rights reserved.