A device for uphill start-up assistance for a motor vehicle including a control for controlling release of the vehicle mechanical brakes that act on the vehicle wheels, so that the vehicle is maintained on the slope when maneuvering uphill without any intervention from the driver on this maintaining condition. The control uses mainly the state of the slope, the interpretation and anticipation of the commands of driver and/or of a central driving member, and the determined instantaneous clutching characteristics. In a preferred embodiment, the assistance device co-operates with an electrical device of the parking brake.