The authors present 20 patients (9 men, 11 women) with erythropoietic protoporphyria (EPP). The diagnosis was made on the basis of photosensitivity and porphyrin analysis. The disease first became apparent in the first years of life. The following acute symptoms were induced after exposure to sunlight: pruritus with or without skin changes, burning, pain and erythema, sometimes with petechiae, vesiculation and, in two cases, systemic symptoms. Chronic skin changes included hyalinosis cutis-like skin lesions, scarring, and also petechiae. Phototesting provoked only subjective symptoms, and none of the skin lesions characteristic of EPP could be induced. Postnatal diagnosis was attempted in three newborns, each of whom had one parent with proven EPP, by measuring the porphyrins in erythrocytes of cord blood. In all three normal porphyrin values were determined, and during an observation period of 3 years none has developed EPP. Therapy with carotenoids has yielded good to very good results in two-thirds of the patients. So far, a diagnosis of EPP has been established in 30 patients in Düsseldorf: one has died of liver cirrhosis and another has liver damage.