Oxyfedrine has a strong lipolytic effect, shown to occur in the intact anesthetized dog as well as in vitro (mesenterial fat pads of the dog). The increase in FFA ob served after injection of 0.5 mg/kg of oxyfedrine was long lasting and abolished by previous administration of nicotinic acid 100 mg/kg, whereas propranolol (1 and 2 mg/kg) only partially blocked this response, although it completely in hibited the lipolytic effect of adrenaline. In experiments conducted in vitro, oxyfedrine induced dose-dependent lipolysis; the effects may be additive with those of adrenaline. They are enhanced by theophylline, not affected by propranolol and abolished by phentolamine. The results suggest that oxyfedrine acts on adipose tissue both through stimulation of β-receptors and through a mechanism unrelated to adrenergic receptors.