INTRODUCTION: Motor performance in Park-inson’s Disease (PD) patients is generally analyzed in laboratory. However, laboratory techniques do not allow estimating long-term ON/OFF fluctua-tion in PD patients. Here, we propose an ambula-tory system based on kinematic sensors that can detect basic body postures during daily activities of the PD patients.METHODS: 10 PD patients with sub-thalamic nucleus deep brain stimulation (STN-DBS) and 10 healthy control subjects participated in a 45 min-utes protocol of typical daily activities. PD patients did the test twice: once with stimulation ON and once with the stimulation OFF. Three kinematic sensors were attached on the trunk and shanks (see Fig.1) to detect basic postures (sitting, standing, lying) and gait periods. Using the shank sensors periods of gait were detected and using the trunk sensor lying periods and also transitions between sitting and standing were detected. Anterio-posteror trunk’s velocity (TV) during sitting-standing transitions as well as transition duration (TD) was estimated. Outcomes were compared to the patients’ UPDRS score.RESULTS: Periods and type of the body postures could be detected with a good accuracy (see Table 1). In PD patients, STN-DBS significantly (p < 0.005) reduced TD (3.27±0.42 vs. 3.54±0.53 sec) and significantly (p < 0.001) increased TV (9.65±2.29 vs. 7.85±2.20 deg/sec). However, both parameters remained significantly (p < 0.05) dif-ferent from the values of the control group (TD = 2.82±0.22 sec, TV = 13.12±2.02 deg/sec). Signifi-cant (p < 0.05) correlation between the UPDRS posture subscore (UPDRS III subscores 27, 28, 30) and TV and TD was found (r = -0.69 and r = 0.69 respectively).DISCUSSION & CONCLUSIONS: An ambula-tory method suitable to monitor daily activities of PD patients has been proposed. System could clas-sify different body postures with a high accuracy. We found that although STN- DBS significantly improved motor performance of the PD patients, their performance remained significantly different from control subjects.ACKNOWLEDGEMENTS: This work was sup-ported in part by Swiss National Science Founda- tion under grant FNRS 3152-062006.00/1.