This paper summarizes the results of three controlled clinical trials related to the transplantation of embryonic ventral mesencephalic tissue into the striatum of 46 idiopathic parkinsonian patients exhibiting motor complications on standard levodopa therapy. From January 1988 to April 1990, 30 subjects with fluctuating Parkinson's disease received fetal dopaminergic tissue implants by the open microsurgical technique. In March 1992 the stereotactic approach was adopted for successive fetal mesencephalic cell suspension transplants (7 unilateral and 9 bilateral) into the caudate and putamen of parkinsonian patients with levodopa-induced complex fluctuations and dyskinesias. The neurological assessment performed 12 months before and 3-18 months after transplantation demonstrated a reduction of both the daily time spent in the 'off' condition and the number of daily 'off' periods, and a significant improvement of the motor scale. The stereotactic selective thalamotomy with microelectrode recording was introduced in January 1993, in order to provide a further potential treatment strategy; i.e., the combination of the two surgical trends in Parkinson's disease, the restorative neurotransplantation technique, and the selective lesional approach. In addition to that, microelectrode recording is also used for implantation site selection and functional characterization.