In this paper we describe a new method for detecting and tracking multiple persons with a stereo camera. The method is based on the idea of the plan-view map, i.e., the 2D histogram of projected 3D measurements from the camera. It estimates the statistical feature in an optimal window, e.g., a rectangular region, on the histogram, considering stereo measurement error, human breadth, and height. Then, it measures the actual statistical feature in the same window on the input histogram and compares estimated feature with measured one to detect and track persons. Experimental results show that our method can achieve higher performance than a normal plan-view map.