Investigations with the electron microscope on peripheral blood of patients with Hodgkin’s disease revealed parallel tubular structures in the cytoplasm of the lymphocytes, similar to those described in the literature. In normal subjects 2–9% of the lymphocytes were found to contain these structures. The number of such lymphocytes is increased in most patients as compared to normals. A correlation between an increase of inclusions containing lymphocytes and the histological or clinical classifications could not be established. An elevation of lymphocytes with tubular structures could be found in both favourable and unfavourable histological and clinical subgroups of Hodgkin patients, but especially in all groups with an unfavourable prognosis. The origin and function of the parallel tubular structures is still unknown, but their increase in lymphocytes of patients with Hodgkin’s disease is of some interest in view of the involvement of these cells.