Both clinical rating scales and objective locomotion measurement are critical evaluation for primate models of Parkinson's disease. Video image analysis system which has been widely used for objective measurement of locomotion behavior for systemic models has rarely been applied to hemiparkinsonian primate model. In this study, a video image analysis system provided by Vigie Primates software was used to assess the locomotion behavior of MPTP hemi-lesioned parkinsonian cynomolgus monkeys by intracarotid infusion. Regardless the presence of only hemilateral abnormal movement, this video image analysis system was sensitive enough to demonstrate a significant difference between normal and MPTP hemi-lesioned animal on several aspects of motor behavior depicted by this software, including quantity of movement, duration spent in activity and count of burst activity Specifically, a newly introduced ratio of duration/count for every type of movements was a sensitive parameter to objectively measure the changes of locomotion behavior in MPTP hemi-lesioned parkinsonian primates. As a result, the ratio of duration/count for the middle activity was decreased and the ratio of duration/count for the freezing activity was increased in MPTP hemi-lesioned animals, which correlated well with clinical rating scores. Our results support that video image analysis system would be a sensitive objective measurement of locomotion behavior for hemi-lesioned parkinsonian monkeys. (C) 2009 Elsevier B.V. All rights reserved.