Typically, the structures represent about 30% of the cost of a reinforced concrete building. In parallel, recent research on high-strength concrete and its application in structural elements have provided new alternatives for the construction of tall buildings. With that, the engineers have to provide, at the same time, more economical solutions, but with the required safety. So, reliability-based optimization models (RBDO) are an interesting tool for this kind of problem, since their objective is always to seek the best compromise between economy and safety. This book presents a RBDO model applied to reinforced concrete to obtain economic structural elements with the required safety. The book orientations are given for reinforced concrete beams and plane frames design in the ultimate limit state (rupture) and in the serviceability limit state (deformations). The proposed model should be interesting for professionals who seek to apply the concepts of probability of failure to determine the safety of structural elements, as well as to those seeking information on structural safety combined with the economy in these kinds of projects.