Two cases of erlotinib-associated acute pneumonitis are described. The first patient was started on erlotinib treatment for metastatic non-small cell lung cancer. The second patient was treated with erlotinib for metastatic adenocarcinoma of unknown origin. Both patients developed dyspnea and hypoxemia five to six days after initiation of erlotinib treatment. In both cases, computed tomography scan of the chest showed extensive bilateral ground-glass infiltrates consistent with pneumonitis. In both patients, acute pneumonitis resulted in respiratory failure requiring intubation and mechanical ventilation. Diffuse alveolar hemorrhage was excluded by bronchoscopy in both cases. Bronchoalveolar lavage cultures were negative. Erlotinib treatment was stopped and both patients were treated with corticosteroids. The first patient improved gradually and finally was discharged to a rehabilitation centre, but unfortunately the second patient died of Klebsiella sepsis. Naranjo causality scale in both cases suggested a probable association between erlotinib and pneumonitis. Literature on erlotinib-associated pneumonitis is sparse. The clinical presentation and radiographic findings of erlotinib-associated acute pneumonitis are described.