Although substantial therapeutic advances have been developed during the last decade, L-dopa remains as the most successful treatment for Parkinson's disease. However, about 80% of the patients show motor and psychiatric complications after several years of levodopa treatment. Thus, new therapeutic approaches have been undertaken during the last decade in order obtain a better control of the motor symptoms. Adrenal medullar grafts into caudate nucleus and/or putamen have been widely studied as a new therapeutic strategy. They have been undertaken in more than 300 parkinsonian patients and the general finding is that adrenal medullar grafts induce a significant improvement of motor symptoms which remain 1 year after the surgery. The mechanisms by which they can elicit a motor improvement are not well understood since chromaffin cells do not survive in the host brain after transplantation as demonstrated by PET scan studies. The present work summarizes the results found by different authors as well as the mechanisms involved in the motor improvement observed in these patients.