This paper presents the analysis of forced vibrations of a cylindrical shell with axisymmetric initial imperfection subjected to hydrodynamic pulsating pressure. The stability of steady state harmonic response is studied with respect to both axisymmetric and asymmetric perturbations. The analysis of stability is based on the nonlinear von Kármán-Donnell equations linearized with respect to perturbations. An interesting conclusion of this paper is that although the axisymmetric steady state motion is linear it can be unstable due to asymmetric perturbations. © 1987 Birkhäuser Verlag.