The proportions of optimum steel plate girders are investigated using a dynamic programming scheme. The optimum properties are determined for realistic steel material and fabrication costs as well as for constant material cost, or minimum weight. Simply supported, uniformly loaded, unstiffened symmetric plate girders are considered. The effect of steel industry pricing practices on the optimum dimensions of a girder are illustrated. The effect of using commercially available plate sizes is also investigated. The optimum geometrical configuration is highly sensitive to pricing practices and available plate sizes; the overall girder weight and cost, however, are rather insensitive to changes in geometry caused by unit material cost differentials.