Forty-three patients with several hematological diseases in the early stage of bone marrow transplantation were prospectively studied. All patients underwent a complete neurological examination, vibratory sense perception test and nerve conduction study both before and after the bone marrow transplantation. The following nerves were studied: median, peroneal, posterior tibial (motor), median and sural (sensitive). Most patients were in busulphan, cyclophosphamide, cyclosporine A, methotrexate and corticosteroids. Although the results showed statistical differences in the nerve conduction study, all of these differences were not sufficient to induce or diagnose peripheral nerve injury. Therefore, it was concluded that drugs used in the bone marrow transplantation do not induce peripheral neuropathy.