Onboard　vehicle　detection　system　is　of　great　importance　to　reduce　vehicle　collision　accident　and　increase　the　driving　safety　on　road.　It　aims　at　detecting　vehicles　appearing　around　the　ego　vehicle　using　vehicle-mounted　camera,　so　as　to　alert　the　driver　about　driving　environments　and　possible　collision　with　other　vehicles.　In　this　paper,　we　analyze　the　detail　difficulties　lying　in　the　problem　and　review　most　of　the　literatures.　A　typical　vehicle　detection　algorithm　includes　two　steps:　hypothesis　generation　and　hypothesis　verification.　After　a　vehicle　is　detected,　it＇s　tracked.　This　paper　introduces　the　principle　of　typical　methods　of　detection　and　tracking　and　analyzes　their　respective　pros　and　cons.　Finally,　we　propose　some　research　directions　in　the　future.　©　2012　IEEE.