A patient with non-Hodgkin's lymphoma (NHL) who developed polycythaemia vera (PV) is reported. Diffuse large-cell NHL was diagnosed and he was subsequently treated with combination chemotherapy including high dose cyclophosphamide and procarbazine. Four and a half years after chemotherapy splenomegaly developed, coincidently with the appearance of high Hb values, RBC and platelet counts. The screening tests for PV were consistent with this diagnosis, while the search for lymphoma activity was negative. To the best of our knowledge, the present case represents the first well-documented instance of PV following NHL.