Large bipolar strain of up to 0.36% (peak-to-peak value) was measured in BiFeO3 ceramics at low frequency (0.1 Hz) and large amplitude (140 kV/cm) of the driving field. This strain is comparable to that achievable in highly efficient morphotropic phase boundary (MPB) Pb-based perovskite ceramics, such as Pb(Zr,Ti)O-3 and Pb(Mg,Nb)O-3-PbTiO3. The strain showed a strong dependence on the field frequency, and is probably largely associated with domain switching involving predominantly non-180 degrees domain walls. In addition, application of an electric field of low frequency rearranges the defects, which act as pinning centers for the domain walls. The resulting depinning of the domain walls leads to a more efficient switching and, consequently, to an increased response. The large strain reported here suggests that the domain-wall motion in BiFeO3 may be as large as in classical lead-based ferroelectrics. We hope that this finding might further stimulate the search of new lead-free MPB compositions based on BiFeO3.