Five patients with usual interstitial pneumonia in 3 generations of one family are described. Included are twin brothers with identical pulmonary lesions, identical minor congenital chest wall deformities, and complicating spontaneous pneumothorax. The observations illustrated all stages of the disease and showed that pathologic and physiologic abnormalities can precede radiographic changes, and all 3 abnormalities can precede clinical symptoms. This report is the first to document father to son transmission of the disease with lung tissue evidence and thereby supports the hypothesis of autosomal dominant inheritance.