Free amino acids were examined in the cerebrospinal fluid from 20 patients with (mean age 67 years) and from 20 old age control patients without pathological clinical neurological findings (mean age Parkinson’s disease 70 years). The levels of the free amino acids were very similar in these two groups of patients, only Tyr, Phe, Try and Arg were slightly elevated in the Parkinsonian patients. On the other hand, these 40 old patients showed an increase of 11 amino acids (Gin, Gly, Ala, Cit, Abu, Val, Met, He, Leu, Phe and Lys) and a decrease of three (PEA, Asp and H.Car) when compared with a younger control group of 19 subjects (mean age 38 years).