We investigated the efficacy and safety of sitafloxacin (STFX) in patients with mild to moderate community-acquired pneumonia or secondary infections of chronic respiratory tract diseases. The results showed that the efficacy rate was 96.5% (111/115) in patients analyzed for efficacy. The efficacy rate by STFX administration method was 93.9% (46/49) at 50mg b.i.d., 100% (37/37) at 100 mg q.d. and 96.6% (28/29) at 100mg b.i.d. In chest X-rays, the image improvement rate in 102 patients with shadows before treatment was 94.1% (96/102). The image improvement rate by STFX administration method was 90.5% (38/42) at 50 mg b.i.d., 97.1% (33/34) at 100mg q.d. and 96.2% (25/26) at 100mg b.i.d. Side effects occurred in five out of 115 patients (4.3%). Abnormalities in hepatic function test values appeared in two patients and abnormalities in renal function test values appeared in three patients. In four cases, the abnormalities were very mild and STFX administration was continued without any treatment. In the other patient, the abnormal value rapidly returned to normal after STFX administration was discontinued. These findings indicated that STFX can be used safety in routine practice by adjusting the administration within the approved dose based on patient characteristics. Good therapeutic effects can be expected in patients with respiratory tract infections.