[en] Gemcitabine pulmonary toxicity is rare and represents a difficult diagnosis. A 61 year old female treated with gemcitabine for a metastatic non-small cell lung cancer (NSCLC) developed during the fifth chemotherapy cycle an acute respiratory distress syndrome with fever, tachypnea, marked hypoxemia and a diffuse interstitial-alveolar infiltrate on chest radiograph. No infectious or opportunistic etiology or cardiovascular disease was demonstrated. Withdrawal of gemcitabine and administration of corticosteroids led to symptomatic improvement. This acute pneumonitis was likely drug induced.