Four 3-phenyl-2-amino-trans-decalin isomers were synthesized in order to obtain derivatives of phenylethylamine with a rigid conformation between the phenyl ring and the amino function. The stereoisomers were tested as inhibitors of catecholamine uptake by rat brain synaptosomes, and their potency was compared with that of amphetamine. The most potent inhibitor of catecholamine uptake was the diaxial 2(a)-amino-3(a)-phenyl-trans-decalin, which was one-fourth to one-third as potent as (+/)-amphetamine. As a dopamine uptake inhibitor in the stiatum, this compound was competitive. The results differ from those obtained earlier with similar analogs with a norepinephrine moiety incorporated into the decalin structure, since a gauche derivative [2(a)-amino-3(e)-3,4-dihydroxyphenyl-3-trans-decalol] was then the most potent and over 20 times as potent as the diaxial anti derivative. It remains to be seen whether this indicates that the mode of binding of phenylethylamines is different from that of catecholamines.