Over the past decade, we have worked with many companies and agencies (including Motorola, US Sprint, Ericsson, Siemens, Bellcore, Kodak, McDonnell Douglas, and the US Naval Research Laboratory) building reusable OO communication software frameworks and applications. In these projects, we’ve applied a range of OO middleware frameworks including OMG CORBA (an emerging industry standard for distributed object computing middleware) and the ACE framework (a widely used C++ framework that implements many strategic and tactical design patterns for concurrent communication software). Some of the important lessons we’ve learned from developing and deploying reusable OO communication software components and frameworks in practice are described here.