Lung agensis is a rare developmental anomaly. It can range from total bronchial and parechymal agensis to mild pulmonary parenchymal hypoplasia of one or both lungs. A case of lobar agenesis of the left upper lung in a 15-year-old boy is presented. The patient had mild exertional dyspnea. Pulmonary angiography revealed the absence of the left upper pulmonary artery and vein. Bronchography showed no branching of bronchus to the left upper lobe. Intravenous pyelography revealed incomplete duplication of the right urinary tract.