The nature of the orientational phase transition in the three-dimensional Lebwohl-Lasher model of liquid crystals has been studied by computer simulation using reweighting techniques and finite-size scaling analysis. Unambiguous numerical evidence is found in favor of a weak first-order transition and the presence of pseudospinodal points, T*, which are extremely close to the equilibrium transition temperature, Tc-T*/Tc0.5×10-3, in good agreement with experimental data for the nematic-isotropic transition.