The (+) isomer of fenfluramine is obtained in the following way: The action of d-camphoric acid on (rac)-fenfluramine (I) forms the camphorate of (+)-fenfluramine (II). After purification of this salt by crystallization, sodium hydroxide in methylene chloride is added, forming (+)-fenfluramine (III) after removal of camphoric acid. Finally, the action of hydrogen chloride in methyl cyclohexane on (+)-fenfluramine produces the corresponding salt: (+)-fenfluramine hydrochloride.