A method for the transmission of data messages in a switched cyclical communication system (38, 39) with a linear or ring arrangement of the users. Real-time critical data messages are transmitted in a first segment (20) of a transmission cycle (31), without the need to first plan the send and receive instants in the forwarding users, such that the chronological start (21) of the first segment (20) of a transmission cycle (31) is guaranteed by all users in all transmission cycles through monitoring. The duration of the first segment (20) of a transmission cycle (31) can be fixedly specified or automatically adjusted using a timeout procedure.