Four weeks after starting treatment he consulted us for a dry cough. Chest X-ray at that time showed no abnormalities. Although dry, nonproductive cough is usually caused by ribavirin, it typically clears after stopping the drug. The dry cough, however, persisted after end of treatment, being the reason to consult a chest physician. Physical examination revealed bibasal crepitations. A new chest radiograph showed bilaterally a diffuse, interstitial pattern ( Fig. 1a) and chest high-resolution computed tomography (HRCT) demonstrated bilateral ground-glass opacities in central and upper zones (Fig. 1b) . Pulmonary function tests indicated a restriction and a diminished diffusing capacity. Maximal incremental cycle ergometry showed decreased breathing reserve (0 l/min), high breathing frequency (65/ min), and exercise-induced hypoxemia caused by an oxygen uptake problem, compatible with interstitial pulmonary disease. Results from bronchoalveolar lavage supported a diagnosis of drug-induced interstitial pneumonitis (cell count 1.68 9 10 9 /L, 73% lymphocytes, CD4/CD8 ratio 0.5). The results of cultures and stains of the bronchoalveolar lavage specimens were negative for bacteria, fungi, acid-fast bacteria, cytomegalovirus, herpes simplex virus, and malignant cells. There were no signs of infection (blood culture was negative).