Lymphogranulomatosis (Hodgkin's disease) is a rare neoplasm in the G.D.R.: incidence (standardized for "Europe-population") male 3.2--3.5, female 1.8--2.1 per 10 000 per year. Geographical differences in incidence and mortality are remarkable, but firm conclusions cannot be drawn. Epidemiological research has demonstrated: familial aggregation; association with HLA-antigen; space-temporal clusters which are considered as suspicious for infectious aetiology; association with occupational factors; higher incidence after tonsillectomy and appendectomy as an index of social factors; no influence of ionizing radiation. Multiple primary malignant neoplasms are strikingly often found in patients with Hodgkin's disease. It may be that Hodgkin's disease is no nosological entity but clinical and morphological manifestation of two diseases, namely infectious granuloma in youth and true neoplasm in the elderly.