In the individually-caged, unrestrained rhesus monkeys, food consumption, spontaneous activities and night-time sleep were measured with a minimum of experimental manipulation. Fenfluramine, chlorphentermine and U-22, 394A (1, 2, 3, 4, 5, 6-hexahydro-6-methylazepino [4, 5-b] indole hydrochloride) were found to reduce food intake in doses that produced no sign of central stimulation. Several derivatives of phenethylamine with parachloro substitution also have weaker stimulant activities at anoretic doses when compared to the non-chlorinated parent compounds.