Community acquired pneumonia(CAP) is the most prevalent disease among pneumonia patients and progressed to severe pneumonia. A retrospective study was performed to evaluate antibiotic regimens according to guidelines of Infectious Disease Society of America. From January to October 2005, chart review of 50 patients with CAP was peformed in terms of microbiology and laboratory data of each regimen. Temperature, WBC count, ALT, AST and alkaline phosphatase of each patient were examined for liver toxicity. In three patients received levofloxacin appeared to have normalized temperature and improved cough. The patients who received cefmetazole -aminoglycoside appeared to have worsen LFT(Liver function test). Many patients in flomoxef-aminoglycoside group received mechanical ventilation because of the basis diseases like tuberculosis, diabetes mellitus and hypertension. In conclusion, antibiotic therapy for the treatment of CAP should be selected according to tolerance, bacteria and severity of disease.