Two technical advantages of ATM, end-to-end QoS and high bandwidth, make ATM suitable for distributed real-time systems (DRTSs). However, ATM capabilities can not be used correctly and efficiently without an adequate mapping of timing constraints of messages onto ATM services. This paper presents an approach for a cc systematic,, mapping of real-time message attributes onto parameters, and quality of service, of ATM connections. This approach is useful for one who needs to develop a distributed real-time application above ATM with a few knowledge of ATM protocols. A message scheduling algorithm based on EDF is used ro deal with the sharing of an ATM connection between several message sources.