Immunohistochemical study with monoclonal antibodies against fast myosin heavy chains showed that excision of a fragment of sciatic nerve does not change, while compression of the nerve decreased the relative content of fast muscle fibers in rat soleus muscle. The content of fast fibers in the muscles of contralateral limbs decreased in both models of denervation. Hence, contralateral limbs cannot be used as the control in experiments with disturbed neurotrophic function. Possible mechanisms underlying changes in the immunohistochemical profiles of experimental and contralateral limbs are discussed.