A study of the wave runup phenomenon on smooth impermeable curvilinear slopes is conducted in order to investigate the effects of various wave parameters and slope characteristics on the runup and wave reflection. Three arbitrary models with different curvature of each circular, elliptical, hyperbolic and parabolic curves are tested with regular nonbreaking waves. An empirical equation is proposed to express the relative runup with nonlinearity. It is found that the relative runup varies with wave steepness, relative depth and relative height.