We report the case of a young man, affected by rheumatoid arthritis who developed a rapid-onset short-of-breath, hemoptysis, and severe weakness, about 2 weeks after the administration of leflunomide. Chest radiography showed central bilateral opacities and pleural effusion as confirmed by the high-resolution computed tomography that demonstrated diffuse ground-glass and interlobular septal thickening as well. On admission at the Emergency Department, a microhematuria and a severe anemia were also documented. On the basis of the clinico-radiologic presentation, a pulmonary hemorrhage was likely to occur; so to clarify the origin of this process, a complete serologic examination was performed but all the antibodies were negative. Finally a renal biopsy was performed and it showed a pauci-immunologic glomerulonephritis and the bronchioloalveolar lavage confirmed the diffuse alveolar hemorrhage. In conclusion, the diagnosis of leflunomide-pulmonary-renal syndrome was rendered. The treatment with leflunomide was suspended; the conditions of the patient gradually improved and he became completely asymptomatic 1 week later.