A method is proposed for the determination of the optimum depth and area of flexural reinforcement for reinforced concrete T-beam sections. To evaluate an objective function, a ratio of steel to concrete costs is necessary. The problem is solved using the Lagrange multipliers method. Three examples are presented to illustrate calculation procedures, and some characteristics of the optimum solutions are considered. The method can serve as the basis for developing general rules for selecting effective depths and reinforcement ratios for T-beams including rectangular sections.