The present study deals with the morphological alterations resulting from the pressure solution of fluid-filled tubular pores embedded in a stressed solid matrix. Building upon previous work concerning transformation kinetics and the kinetically unstable nature of cylindrical solid-fluid phase boundaries subjected to nonhydrostatic stress, we investigate the response of such a pore to circumferential and longitudinal perturbations in its shape by means of a linear stability analysis. We obtain criteria for the onset of instability, determine the wavenumber of the disturbance with fastest growth, and demonstrate that with increasing pore pressure the dominant instability changes from a circumferential to a longitudinal mode. This last feature could distinguish interface migration that is limited by the dissolution/precipitation kinetics from that controlled by diffusion through the pore fluid. We finally obtain estimates of the number and spacing of the inclusions formed when a cylindrical pore breaks up following unstable circumferential or longitudinal growth. ¿ American Geophysical Union 1994