Objectives: Atrial demand type pacemaker such as AAI and AAIR was one of good pacemaker option in patient with sick sinus syndrome. We aimed to verify long term safety and clinical outcomes of AAI type pacemaker in patients with sick sinus syndrome and intact AV conduction system. Methods: We enrolled 131 patients (mean age 66.2짹9.6, male 59.6%) with diagnosed sick sinus syndrome who underwent permanent pacemaker implantation from 2000 to 2008. We checked baseline clinical characteristics, laboratory findings and echocardiographic data. We compared the incidence of death, stroke, hospitalization due to congestive heart failure and pacemaker malfunction according to the type of pacemaker. Results: AAI type pacemaker was implanted in 13 patients(9.9%), DDD type in 76 patients(58%) and VVI type in 42 patients(32.1%). There was no significant difference in baseline clinical characteristics among the types of pacemaker. During clinical follow up, patient with AAI type pacemaker showed low incidence of hospitalization due to congestive heart failure(0% in AAI, 7.0% in DDD, 17.1% in VVI, p=0.040), stroke(0% in AAI, 2.8% in DDD, 14.3% in VVI) compared with VVI or DDD type pacemaker. In echocardiographic examination, incidence of tricuspid regurgitation more than grade II was higher in VVI or DDD type(0% in AAI, 42.3% in DDD, 57.7% in VVI, p<0.001) and LV dyssynchrony defined as more than 60 ms of peak systolic time difference was less frequently observed in AAI type(8.0% in AAI, 68% in DDD, 24% in VVI, p=0.023). In laboratory findings, the level of NT-pro BNP was significant lower in AAI type(251.5짹266.9 pg/mL in AAI, 857.7짹1976.1 pg/mL in DDD, 846.1짹8162 pg/mL in VVI, p=0.032) and serial follow up result of NT-pro BNP showed less frequent increasing tendency in AAI group(0% in AAI, 57.1% in DDD, 75% in VVI). Pacemaker malfunction due to lead dislodgement was observed in 2 cases only with DDD type pacemaker. AV block greater than 2nd degree was not observed in any patients with AAI. Conclusions : Atrial demand type pacemaker showed good safety and favorable long term outcome in patient with sick sinus syndrome.