Earlier investigations of resistive instability have shown that an equilibrium flow, including a flow of the order of the natural diffusion, has a profound influence on the stability properties of the tearing mode. It has been reported that a perpendicular flow of the same order as the natural diffusion (&eegr;/a) makes a finite shift in the stability threshold as &eegr;→0, and only the sign of the velocity matters in this limit. Here the primary concern is with how a moderate or small magnetic Prandtl number changes the stability threshold of a magnetofluid in the presence of a perpendicular flow: it is found that the threshold is again continuous atv=0. The flow is still stabilizing or destabilizing according to the direction of the flow. The viscosity plays important different roles in the static and nonstatic cases. The stability of a static plasma is independent of the magnetic Prandtl number, but the growth rate is not. The stability depends on this number in the nonstatic cases. It is found that the magnitude of the shift in the stability threshold decreases with increasing magnetic Prandtl number. This effect tends to oppose the stabilizing or destabilizing effect of the flow. An increase in the viscosity may in fact destabilize modes when the flow is diffusive. The boundary in parameter space between the inertial and viscous regime is estimated. High‐beta devices are well within the viscous regime. It has been possible to demonstrate that the correction caused by viscosity is far more important than those corrections caused by a perpendicular or a shear parallel flow for modes of finite growth rate.