The optimal plastic design of framed structures has been treated as the minimum weight design while satisfying the limit equilibrium condition that the structure may not fail in any of the all possible collapse modes before the specified design ultimate load is reached. Conventional optimum frame designs assume that a continuous spectrum of member size is available. In fact, the vailable sections merely consist of a finite range of discrete member sizes. Optimum frame design using discrete sections has been performed by adopting the plastic collapse theory and using the Complex Method of Box. This study has presented an iterative approach to the optimal plastic design of plane structures that involves the performance of a series of minimum weight design where the limit equilibrium equation pertaining to the critical collapse mode is added to the constraint set for the next design. The critical collapse mode is found by the collapse load analysis that is formulated as a linear programming problem. This area of research is currently being studied. This study would be applied and extended to design the larger and more complex framed structures.