Steel special moment frame is widely used for multistory building construction in high seismic regions due to its excellent ductility capacity and architectural versatility. To control lateral de ection, design engineers also prefer to use “deep” columns to gain higher exural sti ness. While a signi cant amount of research has been conducted on the cyclic performance of beams and beam-to-column connections, research on columns, especially deep columns, is very limited. This study showed that deep, slender columns were prone to local buckling and signi cant axial shortening, a phenomenon typically not captured in nonlinear nite element simulation. Column global buckling would occur when not only the member slenderness ratio was high but also more compact sections was used that caused signi cant strain hardening. Based on the test results, criteria that would limit the amount of local buckling to ensure su cient column rotation capacities are in development. The implication of column shortening on the collapse vulnerability of multistory steel moment frame buildings is also been evaluated.