Some patients of dermatomyositis (DM) with interstitial pneumonia (IP) have common clinical features. Clinical features of these patients are acute onset, very poor prognosis and that patients have fever, arthritis, typical skin rash, mild myositis and show low ratio of CPK/LDH, low incidence of antinuclear antibody (ANA) appearance, low inflammatory signs. We experienced two cases of this category of DM with IP and examined immunological aspects. Case 1. A 52-year-old woman was admitted in June 1, 1990 with a one-month history of arthralgia and a ten-days history of fever, skin rash, myalgia and dyspnea on exertion. On examination she had Gottron's papules on her fingers, erythema on back, bilateral elbows and legs, proximal muscle weakness and arthritis. Fine crackles were audible in the lower lung fields. Laboratory data included CPK 200 IU/l, ALD 3.2 IU/l, LDH 805 IU/l. Analysis of bronchoalveolar lavage fluid (BALF) revealed increased cellularity with lymphocytosis. She was treated with oral corticosteroid (CS), pulse CS, cyclosporin A. Inspite of these therapies, she died of progressive respiratory insufficiency in July 10, 1990. Case 2. A 23-year-old woman was admitted in April 1, 1991, with a two-month history of arthralgia and a one-month history of fever, skin rash, stomatitis, alopecia. On examination she had Gottron's papules on her fingers, erythema on malar, bilateral elbows and legs, arthritis and stomatitis. Laboratory data included CPK 97 IU/l, ALD 8.5 IU/l, LDH 779 IU/l. She began experiencing dry cough and dyspnea on exertion in May 1991. Analysis of BALF revealed increased cellularity with lymphocytosis. She was treated with oral corticosteroid(CS), pulse CS, pulse cyclophosphamide.(ABSTRACT TRUNCATED AT 250 WORDS)