The recent report by Madrazo and coworkers on the successful treatment of Parkinson's disease using adrenal medullary tissue transplanted to the caudate nucleus has aroused international interest in the procedure. The present article reports our initial experiences with the operation in five patients and discusses the postoperative effects of the procedure, the protocol used to monitor motor performance, and the need for cooperation with the two registries that have been created to follow morbidity, mortality, and efficacy. We intend to alert the neurosurgeon to important side effects, but not to assess the long term efficacy of the procedure. Postoperatively, a number of transient effects were seen in our patients, the most striking being somnolence, delusions, and lack of significant pain in spite of a large abdominal incision. The only complications have been respiratory. After the early postoperative period, gradual improvement of on-off times and Schwab-England disability scores was seen over 20 weeks. Long term cooperative studies are needed to demonstrate the efficacy of this procedure. neurosurgeons doing transplant operations are urged to join the registries so that uniform information can be collected.