The beneficial role of corticosteroid therapy for the treatment of methotrexate-induced pneumonia remains controversial. We report two cases of acute severe interstitial pneumonia induced by methotrexate in patients with non-Hodgkin lymphoma given a polychemotherapy protocol (M'BACOD). The first signs appeared on the eleventh day of the first cycle in patient one and on the tenth day of the third cycle in patient two. The causal implication of methotrexate was based on the history, the clinical and radiological presentation, and the negative tests in both patients: lymphocyte alveolitis with granulomatous lesions on the transbronchial biopsy in patient one and positive leukocyte migration test in the presence of methotrexate in patient two. Early acute respiratory failure required high flow rate oxygen therapy with positive expiratory pressure ventilatory assistance. The course was rapidly favorable both for blood gases and radiographic presentation without corticosteroids. These two cases illustrate that pulmonary disease can be cured without corticosteroids despite severe respiratory failure at onset. This provides a further argument on reservations about using corticosteroids for suspected methotrexate-induced pneumonia.