A thirty-eight-year-old woman presented with typical signs of erythromelalgia: burning, redness, and warm congestion of the extremities. These symptoms occurred after cessation of obesity drug therapy with norephedrine (250 mg/day) continuously over six years. The condition was refractory to treatment with acetylsalicylic acid. It is suggested that erythromelalgia in this case was unmasked by the vasoactive properties of norephedrine. Continuous drug therapy with norephedrine may have led to adaptive adrenergic subsensitivity of vascular smooth muscles. The pathomechanism of primary erythromelalgia is still unknown. Their observations suggest that an enhanced vasodilatation due to an abnormal adrenergic sensitivity may play an important role in the pathogenesis of primary erythromelalgia.