Abstract: /spl Delta/-causal ordering is a communication abstraction designed for distributed applications whose messages (i) have to be delivered according to causal ordering and (ii) have a limited lifetime after which their data can no longer be used by the application. Example of such applications are: multimedia real-time collaborative applications and groupware real-time applications. For such applications, the broadcasting of information is of primary importance. In this paper we propose a simple and efficient /spl Delta/-causal ordering protocol in the context of broadcast communication. By taking into account transitive dependencies on message sends, this algorithm gets a significant reduction in the control information piggybacked on application messages, compared to previous algorithms.