Optimum design of building frames was extensively studied in the 1960s, because analytical derivation of optimal solutions is possible for simple regular frames. Since the 1980s, with rapid development of computer technology, many methodologies and computer programs have been presented for optimizing real-world structures under practical design constraints. In this chapter, we present various optimization results for building frames. A historical review is presented in Sec. 5.1. The uniqueness of optimal solutions is investigated and approximate solutions are searched for in Sec. 5.2. Multidisciplinary optimization and parametric optimization approaches are presented in Sec. 5.3. A heuristic approach to multiobjective optimization is presented in Sec. 5.4, and nally, multiobjective seismic design optimization is discussed in Sec. 5.5.