Employing Biot's theory for wave propagation in a porous solid, the frequency equation for radial vibrations of a poroelastic cylinder is obtained. The frequency equation has been derived in the form of a determinant involving Bessel functions. The roots of the frequency equation give the values of the characteristic circular frequency parameters of the first four modes for various geometries. These roots, which correspond to various modes, are numerically calculated and presented graphically. The results indicate that the effects of porosity are very pronounced.