Future computer environments will include mobile computers which will either be disconnected, weakly interconnected by low speed wireless networks such as GSM, or fully interconnected by high speed networks ranging from Ethernet to ATM. Two key characteristics of such environments are: a heterogeneous processing environment; and rapid and massive fluctuations in the quality of service provided by the underlying communication infrastructure. The first of these issues, i.e. heterogeneity, can be addressed by exploiting emerging distributed systems standards such as the International Standards Organisation Reference Model for Open Distributed Processing (RM-ODP), the Open Software Foundation's Distributed Computing Environment (OSF-DCE) or the Object Management Group's Common Object Request Broker Architecture (OMG-CORBA). Such standards provide applications with uniform computational models for accessing services and enables them to operate over a variety of processor/operating system configurations. The second of these issues, QoS fluctuations, is, we believe, one of the most fundamental problems in the field of mobile computing. We consider this issue and propose extensions to emerging distributed systems standards to support mobile computing.