Four cases of primary non-Hodgkin's lymphoma of the lung are described. Two cases had low and two intermediate grade lymphoma at the time of diagnosis. The patient who had disease for long duration and received pulmonary radiotherapy developed intractable chest infection and died six months after diagnosis; the three patients having short history of disease and treated with surgery and/or chemotherapy have been doing well for 4 to 77 months after the diagnosis. It is concluded that diagnosis of primary pulmonary lymphoma should be suspected in patients with nodular or interstitial lung disease and bronchoalveolar lavage with aspiration cytology should be done to make an early diagnosis.