The study is conducted on 80 patients with acute exacerbations of chronic obstructive pulmonary disease (COPD) is diagnosed on the basis of Anthonosen 1987 in Respiratory Center, Bach Mai Hospital to determine the clinical, subclinical symptoms and cause of COPD with acute exacerbations. Results: Most of patients were male (88.75 percent) over the age of 60 (91.25 percent). Common clinical symptoms: Dyspnea (100 percent), cough (87.5 percent), coughing up yellow sputum or phlegm turbidity (84 percent), rapid breathing 20 times/minute (93.75 percent), alveolar whispering reduced (85.0 percent), hissing/rale sigh (73.75 percent), chest pain (30 percent), tachycardia 100 beats/minute (58.8 percent), fever (32.5 percent), humidity, crackles rale (57.5 percent). Common subclinical symptoms: leukemia increased 10 G/l (60.0 percent), CRP levels blood increased lmg/dl (63.6 percent), dilated alveoli (67.92 percent), average leukocytosis increased (12.08 + or - 5.25 G/l), average CRP levels increased (3.82 + or - 5.37 mg/dl), PaCO2 average increased (76.11 + or - 3.42), PaO2 average decreased (77.44 + or - 3.81), reducing the average of PaO2 (86.23 + or - 1.35), thickness of right atrium (40 percent), pulmonary artery pressure increased on ultrasound (48.39 percent), heart tears (20.75 percent), dirty lungs on X-ray (18.87 percent). Most of patients admitted to hospital in severe or very severe stage (97.5 percent), of which very severe stage is 78.75 percent. The main cause of COPD with exacerbations are respiratory infections (78.8 percent), however, the rate of positive sputum cultures is only 14.52 percent.