<p>A vehicle automatic transmission control system in which based on the determined operating parameters of the vehicle including degree of throttle opening, vehicle speed or the like, a plurality of sets of membership functions of the parameters are established in accordance with a plurality of sets of predetermined fuzzy production rules. Fuzzy reasoning is carried out on the sets of the rules to determine a target gear ratio to shift to. The plural sets of the rules are predetermined hierarchically. One category of rules is directed toward the entire area of shift control, whereas another category of rules is directed toward a specific shift control area such as hill climbing. Further an additional category of rules is provided to presume the driver's intentional condition such as an intention to decelerate. Based on the last category of rules, fuzzy reasoning is carried out to determine the intentional condition. The condition thus obtained is added to the first-mentioned parameters and the second fuzzy reasoning is carried out to determine the target gear ratio on the basis of the first and second category of rules. <IMAGE></p>
