A patient with pulmonary pseudolymphoma whose chest X-ray shadows could be observed for over five years is reported. A 73-year-old man was admitted to our hospital in March 1993, because of abnormal shadows on a chest X-ray film. There was a solitary mass in the left upper lung field and infiltrate in the right middle and lower lung fields. These shadows had been observed on a chest X-ray film in 1988, and had been gradually growing for more than five years. Transbronchial lung biopsy (TBLB) of the left upper lobe mass resulted in a histological diagnosis of pulmonary pseudolymphoma. The shadows showed no change during the next nine months after his discharge. These findings are suggestive of the natural history of pulmonary pseudolymphoma. It seems that the process involved in this case was benign rather than malignant.