The landmark Theme Building at the Los Angeles International Airport was evaluated for seismic loading. This structure is comprised of a reinforced concrete annular core and four steel arches placed at 90-degree orientations. Performance based engineering was used to assess the seismic performance of the concrete core. A detailed mathematical model of the structure was analyzed using site-specific acceleration histories. Analysis showed that the concrete core had insufficient flexural and shear capacity to resist the seismic loading. A comprehensive retrofit strategy consisting of increasing the capacity and lowering the demand was employed. The focus of the seismic retrofit is a tuned mass damper placed at the roof of the structure to reduce the seismic demand. Additional strengthening for flexure and shear are also incorporated in design. The retrofitted structure met its performance goal. Confidence analyses were conducted to assess the probability of reaching non-ductile limit states.