A dynamic bulge testing technique is developed to investigate the biaxial plasticity of sheet materials at intermediate and high strain rates. The main component of this new dynamic testing device is a bulge cell which is mounted on the input bar of a conventional split Hopkinson pressure bar system. This cell is designed such that the input bar is in direct contact with the bulging fluid. Thus, it can be used to apply and measure the bulging pressure. Both quasi-static and dynamic bulge experiments are performed on 0.8 mm thick dual phase steel sheets (DP450). Experimental results are presented for equivalent plastic strain rates ranging from 100 to 700/s. The material parameters of a rate-dependent Cowper-Symonds plasticity model are determined through FE-based inverse analysis.