An information-transfer control system including a bus control unit (3) coupled to a common bus (1), which unit controls the information-transfer through the bus, and a plurality of transmitter/receiver units (2-i) which transfer information mutually through the common bus. The bus includes a transfer-request-signal line (5) coupled to each of the transmitter/receiver units, one or two permit-signal lines (6) or (6-1), (6-2) which permits a transmitter/receiver unit, adapted to deliver a transfer-request signal, to transfer information, an acknowledge-signal line (7) and a transfer-complete-signal line (9). The bus does not include a suppress-signal line which is included in the conventional system. The transmitter/receiver unit receiving a permit signal begins to transfer information when both the permit signal and a transfer-complete signal are over.