Abstract : In the present study, results of a flow visualization study on the flow around a square cylinder with dissimilar leading edges are presented. The radii of the leading edges of the cylinder ‘rsub1/sub’ and ‘rsub2/sub’ are such that the ratio rsub1/sub/ rsub2/subnbsp;is systematically varied from 0 to 1. The flow structures around the cylinder with different leading edge radii particularly the vortex shedding mode and mechanism are investigated. For studies with stationary as well as oscillated cylinder cases, the results are taken at a Reynolds number value of 2100. For the oscillated case, a special mechanism is made to oscillate the cylinders at a desired amplitude and frequency. That is, the cylinder undergoes forced oscillation in this case. Results indicate that dissimilar leading edges bring notable changes in the near-wake flow structures of a square cylinder. For the stationary cylinder cases, the vortex formation length decreases with increase in the rsub1/sub/ rsub2/subnbsp;ratio. Flow structures are also found to be influenced by the amplitude ratio (amplitude to body size ratio); the higher the amplitude, the larger the size of vortices shed per cycle of cylinder oscillation. In view of marine structures and building sections with similar geometries, the present results carry considerable practical significance.