186 patients in 4 centers will be enrolled in this study. Patients accord with the criteria of CAP with aspiration factors will be enrolled and randomized to one of the following groups. The treatment duration will range from 2 to 4 weeks.

Study Group: Intravenous treatment with moxifloxacin 400mg i.v. OD. Based on investigator's decision, a switch can be made to moxifloxacin 400 mg OD, orally (Moxifloxacin injection will be used no more than 3 weeks consecutively) .

Control Group: Intravenous treatment with levofloxacin 400mg i.v. OD plus metronidazole 0.5g i.v. bid. Based on investigator's decision, a switch can be made to levofloxacin 400mg OD plus metronidazole 0.2g tid, orally.

Treatment should be continued until complete resolution of the radiological, clinical and laboratory alterations or until no further regression can be observed. Clinical, bacteriological, laboratory and radiological examinations will be performed pre-treatment. Swallowing/coughing reflection test will be used for aspiration factor diagnosis. Risk factors (Decreased level of consciousness, dysphagia, gastroesophageal reflux, neurologic disease, mechanical and device-related (e.g. nasogastric feeding tube) impairment of upper aerodigestive tract, vomiting, bronchial obstruction due to neoplasm or foreign body, bronchiectasis, pulmonary infarction, etc) will be evaluated before the treatment. Clinical and laboratory examinations such as blood routine(including Hb, differential blood count, etc), urine routine, biochemistry examination (including serum bilirubin, hepatic/renal function parameters, etc), coagulation examination will be repeated selectively. Radiological examination (e.g. chest x-ray) will be repeated at each visit for clinical monitoring after one week treatment. At the test-of-cure visit (7-14 days after the end of therapy) comprehensive clinical, bacteriological and laboratory examinations will be performed.