Corresponding problems of the radiation forces acting on a rigid spherical obstacle in a progressive plane or spherical sound field have been examined previously [L. V. King, Proc. Roy. Soc. (London)A147, 212–240 (1934); T. F. W. Embleton, J. Acoust. Soc. Am.26, 40–46 (1954)]. In these cases the sound field and scattering obstacle both have symmetry about the line joining the center of the obstacle to the source of the sound field, but for a cylindrical field there exists only a lower degree of symmetry. A more general expression has now been obtained for the radiation force in terms of the complex amplitudes of spherical harmonics required to synthesize the incident sound field—for the cases of greater symmetry this reduces to the simpler expressions previously obtained. The first 20 nonzero amplitudes have been evaluated for a cylindrical sound field, and it is shown that the force is one of attraction near the source, becomes zero at a certain distance, and at a greater distance is a force of repulsion. This is qualitatively the same as for spherical waves, but for any given size of obstacle or frequency of the sound field the point of zero force is always nearer to the source in a cylindrical field. Experimental results will be reported.