Three buildings in Montreal were designed for different levels of "ductility" according to the 1990 National Building Code of Canada and the 1984 Canadian Standards Association standard for the design of concrete structures for buildings. Analytical procedures were developed in order to predict the responses of main structural components to the combined loading effects of axial load, moment, and shear. In addition, a hysteretic behavioural model was developed in order to account for strength and stiffness degradation as well as pinching of the hysteretic response. Nonlinear dynamic analyses were carried out on each building for a series of artificially generated accelerograms together with real earthquake records. The results of the nonlinear dynamic analyses enabled an assessment of the performance of different building designs and an assessment of current code requirements. Key words: seismic design, reinforced concrete, detailing, structures, codes.