To investigate pulmonary involvement in immunoblastic lymphadenopathy (IBL), we report five cases of IBL and 21 other reports from the literature published in Japan. Three of the present patients had respiratory symptoms and showed hypoxemia on admission. Radiographic findings in the present cases showed bilateral mediastinal and hilar lymphadenopathy (LA: 4/5), pleural effusion (PE: 5/5), interstitial shadow (Int S: 1/5), alveolar shadow (A1S: 2/5), and atelectasis (1/5). In the present cases and those previously reported in Japan, the following radiographic findings were observed; LA (56%), PE (40%), Int S (52%), and A1S (24%). Atelectasis was reported only in the present cases. The nine patients with Int S consisted of four with interstitial pneumonia and five with bronchopneumonia. Four of five patients with bronchopneumonia had an opportunistic infection (three had pneumocystis carinii and one had cytomegalovirus). Among the five patients with A1S, two had interstitial pneumonia and the others had bronchopneumonia. Pulmonary involvement was frequently seen in patients with IBL, and may be an important determinant of the outcome of the disease.