Thin films of laser molecular-beam epitaxy grown ZnO films were studied with respect to their optical properties. 4-K reflectivity was used to analyze various samples grown at different biaxial in-plane strains. The spectra show two structures at ≈3.37 eV corresponding to the A-free exciton transition and at ≈3.38 eV corresponding to the B-free exciton transition. Theoretical reflectivity spectra were calculated using the spatial dispersion model. Thus, the transverse energies, the longitudinal transversal splitting ( E LT,), the oscillator strengths, and the damping parameters were determined for both the A- and B-free excitons of ZnO. As a rough trend, the strain dependence of the energy E LT for the A-excitons is characterized by a negatively peaking behavior with a minimum around the zero strain, while E LT for the B-excitons is an increasing function of the strain field values.