Eigenvalue buckling of cylindrical shells with various boundary conditions under hydrostatic load is examined, using an energy method. Results are compared to known solutions, where these solutions exist. It is found that, for shells of intermediate length, buckling loads for different end conditions may be determined by applying a simple, scalar multiplier to the pin-ended case. This does not apply to long shells, where: the circumferential wave number n less than or equal to 3. For n = 2, the ring equation may be applied to all cases, as the boundary conditions no longer influence the solution. It is seen for the case of a shell with one end pinned and the other end free that the buckling solution collapses to the long shell solution, for geometries of practical interest, The effect of radial elastic restraint at the open end is also examined, as an intermediate case between pinned and free ends. The work has application to the design of suction caissons, where cylinder dimensions are usually in the range of intermediate length shells. (C) 2000 Elsevier Science Ltd. All rights reserved.