An improved feed and control system for an internal combustion engine able to be fed with one or other of two fuels such as petrol and liquid gas or petrol and methane, the engine comprising a plurality of first members for introducing a first fuel into corresponding explosion chambers and a plurality of second members for introducing the second fuel into the explosion chambers, the first introduction members being commanded and controlled by a control unit which, on the basis of preselected parameters, acts on the first members such as to achieve optimum engine operation. The control unit also commands and controls the plurality of the second introduction members which feed the second fuel to the respective explosion chambers, the unit hence being the only unit for controlling the engine operation, independently of whether it is operated with the first or with the second fuel.