[en] Some of the biochemical and biological properties of a radioactive analogue of dopa have been studied. [¹⁸F]3,4-Dihydroxy-5-fluorophenyl-alanine (fluoro-dopa) was injected into mature rats, and the relative intracerebral distributions of its amino acid and catecholamine metabolites were comparable with those of the metabolites of [¹⁴C] dopa. The high relative concentration of fluorinated amines in the caudate nucleus supported the proposition that the addition of fluorine in the 5-position on the aromatic ring of dopa does not substantially alter its intracerebral behaviour, and in addition intraperitoneal injection of [¹⁸F] fluoro-dopa or of dopa to reserpinized mice produced similar transitory states of arousal. A technique were therefore developed for the study of the intracerebral accumulation of [¹⁸F] fluoro-dopa. Pre-treatment of a conscious female baboon with reserpine, which reduces dopamine accumulation, produced a strikingly different pattern of intracerebral accumulation of ¹⁸F from that in the control, where a progressive increase in the amount of ¹⁸F recorded suggested the formation and storage of fluorodopamines. The technique is of potential application in the study of intracerebral dopamine metabolism in man. (U.K.)