Protocol conformance test is used to promote the interoperability of protocol implementations developed by venders. Non-interoperability between protocol implementations may be caused by ambiguity and/or misinterpretation of protocol specifications by vendors or by different implementations using different options in specifications. The conventional method used for protocol conformance test has been standardized by ISO/IEC JTC1 and ITU-T with the purpose of determining whether a protocol implementation conforms to its specification. However, the conventional method sometimes gives wrong test results because the test is based on static test sequences. This problem is caused by some failed transitions of a protocol's finite state machine included in a test sequence, which have an effect on the test result of transitions to be tested. In this paper, an approach called dynamic conformance test method (DCTM) is proposed to solve this problem. DCTM dynamically selects different test sequences during testing depending on whether alternative paths without failed transitions exist. As a result, the fault coverage of DCTM is better than that of the conventional test method. DCTM has been implemented and applied to the TCP protocol in order to demonstrate its improvement in the fault coverage compared to that of the conventional method. (C) 2002 Elsevier Science Inc. All rights reserved.