CASE PRESENTATION: A 33-year-old Hispanic male presented to our institute with dyspnea. Past medical history was significant for Diabetes Mellitus type I and end stage renal disease (ESRD) on hemodialysis. He reported recent use of Cannabis. Patient was in mild respiratory distress, afebrile with oxygen saturation of 84% on room air. Physical exam was positive for diffuse rales. Arterial blood gas revealed low pO2 and high A-a gradient. Laboratory workup revealed hemoglobin 8.7g/dl, WBC count 9800/mm3, platetlets 387000/mm3 and INR 1.1. Chest radiograph and CT scan showed diffuse bilateral patchy opacities (Fig. 1). Bronchoscopy demonstrated increased hemorrhagic patterns on serial bronchoalveolar lavage (BAL) (Fig. 2). Cytology showed abundant hemosiderin laden alveolar macrophages. BAL bacterial, viral, fungal, AFB and Pneumocystis jirovicii cultures were negative. Rapid influenza test, anti-Streptococcal antibody (Ab) and Legionella pneumophila antigen were negative. Echocardiogram revealed normal ejection fraction with no mitral stenosis. Antinuclear Ab, antineutrophil cytoplasmic Ab, glomerular basement membrane Ab, cryoglobulins, antiphospholipid Ab and rheumatoid factor were all negative. Serum toxicology screen performed on admission was positive for tetrahydrocannabinol (THC) with value of 163ng/ml (cutoff: 5ng/mL) and negative for cocaine. Patient left the hospital against medical advice and presented in 5 days with hemoptysis and worsening dyspnea, there was a drop in hemoglobin to 7.1g/dl. He was transfused one unit of packed red blood cells and managed supportively with supplemental oxygen. Again, he reported smoking Cannabis but denied cocaine use.