A control system for an automatic transmission, which can easily achieve a variety of shift patterns according to the taste of a driver and the situations of a running road. The control system comprises: a neural network; and a mode switch means for switching a teaching mode and an automatic mode. The neural network learns in the teaching mode and neuro-computes to output a gear ratio in the automatic mode. Further comprised are: tolerance error compute means for computing a tolerance error on the basis of at least one of th propriety of a teaching gear ratio, the ambiguity of an input value and the ambiguity of the teaching gear ratio; pattern produce means for producing a learning pattern; and combined load correct means for correcting the coupled loads of the neural network on the basis of the pattern produce means.