The aim of this paper is to investigate the role of microscaleinertia in dynamicductilecrackgrowth. A constitutive model for porous solids that accounts for dynamiceffects due to void growth is proposed. The model has been implemented in a finite element code and simulations of crackgrowth in a notched bar and in an edge cracked specimen have been performed. Results are compared to predictions obtained via the Gurson-Tvergaard-Needleman (GTN) model where micro-inertiaeffects are not accounted for. It is found that microscaleinertia has a significant influence on the crackgrowth. In particular, it is shown that micro-inertia plays an important role during the strain localisation process by impeding void growth. Therefore, the resulting damage accumulation occurs in a more progressive manner. For this reason, simulations based on the proposed modelling exhibit much less mesh sensitivity than those based on the viscoplastic GTN model. Microscaleinertia is also found to lead to lower crack speeds. Effects of micro-inertia on fracture toughness are evaluated.