In this paper we present \sc Mdtl, a distributed temporal logic for reasoning about both synchronously and asynchronously communicating modular object systems. \sc Mdtl is an extension of \sc Dtl reflecting besides synchronous communication and non-determinism also concurrency and supporting asynchronous communication. It is based on $n$-agent logics. Formulae written in \sc Mdtl are interpreted over labelled prime event structures. A model construction for (a)synchronous concurrent composition has been provided in previous work. The model theory together with \sc Mdtl allows a whole range of issues, like reasoning and verification.