Pressure influences echo intensities of swimbladdered fish through changes in swimbladder volumes and surface areas. Volume reduction is expected to correspond to Boyle’s law (volume ∝pressure−1) but the resulting deformation in swimbladder surface area will largely determine target strength at geometric scattering frequencies. Dorsal and lateral radiographs of juvenile walleye pollock (Theragra chalcogramma) in a pressure chamber were used to image swimbladders from ambient to a maximum of 5-atm pressure. As pressure increased, dorsal swimbladder surface areas decreased at a constant rate among the three individuals. Swimbladder volume reduction rates were similar among individuals but less than that predicted by Boyle’s law. Compression of swimbladders occurred dorsal-ventral, anterior-posterior, and laterally. Resulting swimbladder shapes became more spindlelike as pressure increased. KRM predicted target strengths at 38 and 120 kHz decreased more rapidly at 3 atm above ambient than at lower pressures. [Work supported by ONR and NRIFE.]