Synthesis and release of 3H-dopamine (DA) were estimated by incubating slices of rat striatum with 3,5- 3H-L-tyrosine and by measuring the 3H-amine accumulation in slices and incubating medium at the end of the incubation. Absolute 3H-DA synthesis was estimated by measuring the 3H-water quantities formed during the conversion of 3,5- 3H-L-tyrosine to 3H-dopa. Amantadine pretreatment increased both 3H-DA synthesis and release. This drug effect on striatal dopaminergic terminals is discussed with respect to its utilization in human Parkinsonism.