Asymmetric building structures exist in modern construction to satisfy functional andrnarchitectural requirements. This asymmetry is the main reason for the failure ofrnreinforced concrete buildings unless it is designed to accommodate the response ofrnstructures when subjected to different loadings. rnIn this paper one form of plan irregularity i.e. torsional irregularity condition is studiedrnunder the equivalent static torsional provision of EN 1998-1:2003. Three-storyrntorsionally flexible reinforced concrete buildings subjected to seismic action are studiedrnusing both response spectrum and equivalent static method of analysis. Both methods arernused through the analytical study of 30 random samples and analyses of 2 test modelsrnusing ETABS. The response spectrum method of analysis is used as a reference method.rnTherefore the response of the structures computed using the equivalent static methodrnshall be equal to or greater than the response computed using the response spectrumrnmethod. However, the result shows, the equivalent static method underestimates thernresponse of structures when torsional irregularity exists. This means the response of thernfundamental mode only becomes inadequate because higher modes turn into significant.rnIn such situations, a modifying factor that magnifies the response of an equivalent staticrnanalysis method shall be used. Hence the application of the torsional provision shall bernlimited to torsionally regular buildings or the modification of the analysis method shallrnbe used while the irregularity occurs.