The main purpose of this paper is to present both the fundamental and some higher natural frequencies of noncircular arches with variable cross-section. The nondimensional differential equations governing planar free vibrations for these arches are derived in which the rotatory inertia is included. The parabolic prime arches with three kinds of cross-sectional shapes are applied in numerical examples. And both hinged and both clamped ends constraints are considered. The frequency parameters are reported as the functions of nondimensional system parameters; the rise to span length ratios, the slenderness ratios and the section ratios. The effects of rotatory inertia and cross-sectional shapes on natural frequencies are reported and some typical mode shapes are also presented.