We report a case of primary T-cell non-Hodgkin's lymphoma of the lung. A definite diagnosis was made histologically at open lung biopsy. Atypical cells in the biopsy specimen reacted with monoclonal T-cell markers. Transbronchial lung biopsy and bronchoalveolar lavage fluid were useful in the diagnosis. Primary T-cell lymphoma of the lung is rare and is reviewed in this report.