NiAl single crystals were deformed in soft orientations inside a high-voltage electron microscope. At room temperature, dislocations with <100> Burgers vectors move on 100, 110 and 210 planes and bow out between jogs. The shape of the bowing is determined by anisotropic line tension. The local effective stress calculated from the bowing is somewhat smaller than the resolved shear stress quoted in the literature. Viscous motion between the stable positions hints at the additional action of the Peierls mechanism. Above about 400^°C, the dislocation motion is smooth. It is suggested that it is controlled by diffusion processes.