between potencies for inhibition of uptake and for inducing release were observed for these and additional substrates. The excellent correlation of efficacy at stimulating release versus K/IC ratios suggested thresholds of binding/uptake ratios above which compounds were likely to be substrates. Based on their potencies at hDAT, most of these compounds have potential for abuse and addiction. 4 -Bromomethcathinone, 4-MEC, 5-methoxy-methylone, ethylone, and MDAI, which have higher potencies at hSERT than hDAT, may have empathogen psychoactivity.