Fourteen substances from the class of drugs sometimes known as “legal highs” were screened against a battery of human receptors in binding assays, and their potencies as inhibitors of monoamine uptake determined in functional in vitro assays. Thirteen of the test substances acted as inhibitors of monoamine uptake at submicromolar concentrations, including 9 potent inhibitors of the dopamine transporter (DAT), 12 potent inhibitors of the norepinephrine transporter (NET) and 4 potent inhibitors of the serotonin transporter (SERT). Seven compounds acted as submicromolar inhibitors of both DAT and NET, and three substances 1-(benzofuran-5-yl)propan-2-amine (5-APB),1-naphthalen-2-yl-2-pyrrolidin-1-ylpentan-1-one hydrochloride, (“naphyrone”) and 1-naphthalen-1-yl-2-pyrrolidin-1-ylpentan-1-one hydrochloride, (“1-naphyrone”) were submicromolar inhibitors of all three monoamine transporters. There was a lack of correlation between results of functional uptake experiments and in vitro binding assays for the monoamine transporters. There was also no correlation between the human behavioural effects of the substances and the results of bindings assays for a range of receptor targets, although 1-(benzofuran-5-yl)propan-2-amine(5-APB), 1-(benzofuran-6-yl)propan-2-amine hydrochloride(6-APB) and 5-iodo-2,3-dihydro-1H-inden-2-amine hydrochloride,(5-iodo-aminoindane) exhibited