The effect of phlebotomy therapy on porphyrin metabolism was evaluated in 5 patients with porphyria cutanea tarda symptomatica (PCT-S). The removal of 2,500 to 4,500 cc over a 3 to 41/2 month period resulted in a marked reduction in urine and fecal uroporphyrin excretion in 3 of the subjects. Clinical improvement accompanied the chemical response in each case. In one patient, the induced chemical and clinical remission persisted for 6 months without further treatment.