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