We describe a real-time interprocess communication service (RT-IPC) suitable for distributed systems built over ATM networks. This location-transparent communication service offers end-to-end quality of service guarantees, and end-to-end priority propagation. It relies on a specific realtime ATM Adaptation Layer (AAL-RT), that grants to preempt the transmission of a low priority message by a higher priority one, and on a transport service in charge of QoS negotiation, setup of the ATM virtual channel and priority inheritance. The RT-IPC service is implemented in the Chorus distributed operating system, as servers running in the micro-kernel address space. It is used for the realtime communication within ANTARA real-time clusters, and grants to communicate at a user rate up to 130 Mbps, over 155 Mbps ATM links. The end-to-end transfer delay between participants is less than 400 µs.