This report describes methods for the vibration analysis of side walls of liquid filled tank in ships. The natural frequencies of simply supported side walls are obtained by means of analytical energy method and boundary element method combined with structural finite element techniques. Comparing the results, the numerical accuracy of natural frequencies depending on the mesh sizes has been investigated. The vibratory responses of side walls are also analyzed in the cases where the tank is enforced to vibrate in horizontal or vertical direction with given acceleration. Simplified methods are proposed for the prediction of natural frequencies and acceleration levels of side walls using non-dimensional parameters which are found to be applicable to the problem of both side wetted bulkhead wall.