This paper addresses the problem of interoperability testing for communication protocols. We develop a coherent framework of interoperability testing in which the notions of interoperability, interoperability testing, interoperability test case and interoperability test architecture are interrelated and a systematic interoperability test suite derivation method based on the framework, The approach to interoperability testing is illustrated with the example of the ATM Signaling Protocol. To demonstrate practicality of the approach, we implemented executable test suites derived by the method on a commercial ATM test platform, applied them for interoperability testing of various ATM equipment and analyzed the testing results. (C) 2000 Elsevier Science B.V. All rights reserved.