The problem of buckling of a thin circular ring under uniform external transverse loading is investigated for the force normal to the deformed ring, the force parallel to its initial direction, and the force directed toward the initial center of curvature. Results are derived through a simple treatment within the framework of thin ring theory and without the assumption of inextensionality. It is assumed that the uniform pressure is applied quasistatically, the material is linearly elastic, and the strains are small while the rotations are moderate. In addition, the effect of transverse shear deformation is included.