The possibility that {112} planes in 3.25% silicon iron are active slip planes is investigated. This is found to be the case for certain axial orientations when the deformation temperature is above approximately 184°K. Below this temperature, the {110} plane is the observed operative slip plane. Utilizing a dislocation site etch‐pitting technique and a method of introducing dislocations into the material devised by Stein and Low, measurement is made of the velocity of edge‐type dislocations on {112} planes in 3.25% silicon iron single crystals. The velocity of these dislocations is found to be very sensitive to the applied stress in the range of velocities examined which is from 10−7to 10−2cm/sec. Three temperatures of testing are investigated: 198°, 233°, and 298°K. A method for the determination of the operative slip plane in 3.25% silicon iron as a function of the deformation temperature and the orientation of the deformed samples is proposed. This results in the observation that the stress to cause any given dislocation velocity increases more rapidly with lowering deformation temperature when slip occurs on {112} planes rather than on {110} planes.