A study has been made of the uptake and release of [G-3H]-2-amino 6,7-dihydroxy-1,2,3,4-tetrahydronaphthalene (ADTN) by crude striatal synaptosomes of the rat. 2 Uptake was rapid, temperature-dependent and could be suppressed by a variety of metabolic inhibitors. 3 The Michaelis-Menten kinetincs indicated the presence of two distinct transport systems in the striatum which were of much higher capacity than those found in the cerebellum, which lacks dopaminergic innervation. 4 Uptake of [3-H]ADTN was strongly inhibited by dopamine and the two potent dopamine-uptake inhibitors, benztropine and nomifensine, but only weakly by imipramine and amphetamine (the latter in non-reserpine-treated animals). 5 Accumulated [3-H]ADTN could be released from striatal slices by elevated K+. A similar release was evoked upon the addition of the ionophore, A23187. 6 The most potent releaser of [3-H]ADTN was (+)-amphetamine. This effect occurred at concentrations inactive against ADTN uptake. The neuroleptic cis-flupenthixol produced an inhibition of the spontaneous release. 7 It is concluded that [3-H]ADTN is accumulated preferentially into areas of the rat brain rich in dopamine. The pharmacological specificity of the uptake suggests that it is a good substrate for the dopamine carrier. Following uptake, [3-H]-ADTN may be released by K+ and a calcium ioniphore, which raises the possibility that ADTN might act as a false transmitter.