A method of individual vehicle detection using grayscale images acquired from a high position is proposed for guidance of incoming vehicles to vacant cells in a parking lot and other similar purposes. With the proposed method, each image region corresponding to a cell is fragmented according to density (gray level), and the distribution of segment area is analyzed to decide if a vehicle is present. Reference images taken in vacant state are not needed, hence the method can be easily applied to parking lots in continuous service. Shape features are not employed, hence detection is performed independent of car shape. The proposed method was tested on an actual outdoor parking lot during 4 days with different weather conditions from sunrise through sunset. The results confirmed the efficiency of the proposed method, with the detection rate being over 98.7%. © 2001 Scripta Technica, Electron Comm Jpn Pt 3, 84(10): 25–34, 2001