Remote Procedure Calls (RPCs) realize client-server interactions via a request-response message-passing protocol. They simplify distributed application programming by eliminating the need for explicitly having to code the details of a remote interaction. However, none of the existing RPC implementations are designed to work properly for Delay/Disruption-Tolerant Networking (DTN) where network connectivity is periodic, intermittent, and prone to disruptions. In this paper, we present DTN- RPC, a new approach to provide RPCs for DTN environments. DTN-RPC relies on (a) control and data channels to cope with potentially short contact durations in DTN where large amounts of data cannot be transmitted, (b) explicit and implicit modes to address remote servers, (c) Non-DTN and DTN transport protocols for issuing calls and receiving results, and (d) predicates that servers check to decide whether a procedure should be executed. The implementation of DTN-RPC is based on Serval, an open-source, disruption-tolerant wireless ad-hoc networking system. Our experimental results indicate that the measured CPU and network overheads for DTN-RPC are reasonably low so that it can be executed on smartphones or routers, and that the round-trip times and the number of successful RPCs are highly satisfactory in dynamic networks with unstable links.