An automatic steering system for agricultural tractors was developed using a network of seven microcomputers for the feedback controller. The computer hardware and software which comprise the feedback controller and design considerations in developing a computer network are discussed. Safety requirements of a manual/automatic steering system are presented, and the hydraulic circuit designed for operation with both manual and automatic inputs is described. The steering system uses sonar devices for position sensing. The sonar measuring system is temperature compensated to be reliable from -5° to 55° C. The steering system requires additional development to refine the steering gain function and optimize the position sensing technique.