Protoporphyrinogen oxidase activity and ferrochelatase activity have been measured in blood lymphocytes from patients with prophyria variegata, and from some members of the family of one patient; the mean activity of protoporphyrinogen oxidase from patients was about 50% of that in lymphocytes from normal subjects; similar results were obtained from asymptomatic carriers in two generations of the patient's family. This finding confirms that a protoporphyrinogen oxidase decreased activity reflects the primary genetic defect in Porphyria Variegata. Data of ferrochelatase activity have been found usually in the normal range and these results are discussed.