Abstract | This paper presents the probabilistic assessment of a three-storey steel structure, designed as a benchmark case of the SAC steel project for the Los Angeles area. The seismic behaviour of the structure is here assessed using 2-D dynamic inelastic time-history analyses, accounting for global P-∆ effects, contribution of the interior gravity frames and P-M interaction. The building is subjected to a suite of ground records, which form part of the common seismic scenario for the applications of the LessLoss Sub-Project 9. Ground motions are scaled according to the spectral acceleration at the building’s elastic fundamental period. Randomness associated with material variability as well as the effect of connection fractures are included in the model. Fragility curves are generated using the Monte Carlo simulation method in conjunction with the Latin Hypercube sampling technique in order to reduce the variance in the probability estimates. The failure probabilities are presented in terms of interstorey drift limits at different performance levels. The results of the study show that the ground motion characteristics have a significant effect on the fragility curves, especially at high levels of spectral acceleration and hence nonlinearity.