A number of mid-height steel buildings have been erected recently in Bogotá. Their seismic risk might be high, given the new microzonation of Bogotá and the lack of previous studies; remarkably, the response reduction factors were commonly obtained from general recommendations. The objective of this work is to investigate the seismic performance of these buildings. This study is carried out on eighteen representative buildings. All these edifices have plan symmetry and are uniform along their height. Span-length: 6 ¿ 8 m; number of floors: 5, 10, 15. Earthquake-resistant systems: moment-resistant frames, concentrically-braced frames and eccentricallybraced frames (using chevron braces). For each building, eight seismic zones have been considered. The vulnerability has been evaluated by “push-over” analyses. In the moment-resistant frames and in the eccentrically-braced frames the nonlinearities are concentrated in the plastic hinges near the connections; in the concentrically-braced frames the nonlinearities are allocated in the braces.