34 Patients with an ascertained porphyria cutanea tarda who underwent a long-term therapy a comprehensive internal and hepatological diagnosis was made. In these cases for the first time the estimation of the intrahepatic distribution of enzymes and its comparison with the serum enzymes were also performed. The liver histology allowed a division of our patients into three groups, in which cases the reactive hepatitides prevailed and a conspicuously large proportion of normal histological findings were present. The comparison of all data got with the literature made the conclusion possible that the phlebotomy therapy as well as the care in a special dispensary for years lead to very favourable results on liver and skin.