'"Ownership is less important than market structure in determining the performance (success) of firms” is the argument of this paper. It starts by defining the relevant terms. Secondly, it briefly distinguishes monopoly and perfect competition, being pertinent terms concomitant with market structure. It then proceeds to compare efficiency of a firm in a monopolist industry with that of a firm in perfectly competitive industry, both operating under the same cost and demand conditions. The significance of ownership to efficiency is then explored, followed by a discussion of managerial control mechanisms under either type of ownership. This is followed by a conclusion