The material studied was commercial pearlitic steel deformed by cold drawing. Internal stresses appearing due to the plastic interaction of cementite and ferrite phases of the lamellar pearlite (interphase stresses) were examined in order to clarify the mechanisms controlling plastic behavior of the lamellar pearlite. It was shown that, while the interphase stress level is high at relatively small drawing strain, it is significantly reduced with true strain increasing up to e = 2. The high level of the interphase stress is restored after annealing of the heavily drawn wire and its repeated straining. This result is considered to support a suggestion that the reduction of interphase stress under severe cold drawing is caused by a transformation of the cementite lamellae substructure.