The Tail Suspension Test (TST) is a commonly used screening method for antidepressants properties of drugs in mice. To date, immobility in the TST was scored live, by an observer, or automatically, using devices in which mouse movements were detected by a strain gauge. In this study we tested whether the EthoVision video analysis system can be used reliably and accurately for automatic recording and scoring of duration of immobility in the TST. First, the duration of immobility in two mouse lines was assessed. Different mobility thresholds of the video analysis system were applied and the results compared with the duration of immobility scored manually. Next, the selected immobility threshold was applied to determine the dose-response curves for the drug venlafaxine. Finally, scores from the video analysis system were compared with scores generated by an electromechanical strain gauge device (Med Associates) and a human rater. It was found that the EthoVision system could reliably and accurately quantify the duration of immobility in the TST. The best setup was an immobility threshold ranging from 2 to 3 percentage change in the object area. The EthoVision system was effective in detecting the differences between the mouse lines and the dose response to venlafaxine. The results obtained using the video analysis system were similar to the scores yielded by a human rater and the strain gauge device.