The primary amines 3,4-methylenedioxyamphetamine (MDA), and 1-(1,3-benzodioxol-5-yl)-2-butanamine (BDB) were measured for efficacy in release of [3H]serotonin (5-HT) from rat hippocampal slices, and release of [3H]dopamine (DA) from rat caudate nucleus slices. The N-methyl derivatives of MDA and BDB, MDMA and MBDB, respectively, and the optical antipodes of these four agents were compared in this paradigm. All of the test compounds demonstrated a similar efficacy of [3H]5-HT release in the micromolar concentration range. No significant stereoselectivity was seen in measurements of 5-HT release. However, striking differences were found between the test compounds when [3H]DA release was studied. N-methylation of racemic MDA resulted in a decreased ability to release DA, while side chain extension from alpha-methyl to alpha-ethyl completely abolished this activity. Stereoselectivity for the S-(+)-isomers of MDA and MDMA was also demonstrated in the DA release studies. Correlation of these biochemical findings with human subjective reports indicates that serotonin release may play a more important role in the mechanism of action than does dopamine release.