Regression testing (RT), testing software with previously used test cases, is a mainstream practice in software maintenance. Regression test selection (RTS) is to reduce the number of tests which need to be retested. Safe RTS techniques add the assurance that no modification-revealing test case will be left unselected. Several effective safe RTS techniques were developed for traditional applications, but none of them can be directly applied to Web services, even though there have been RT tools and techniques for Web services test-case generation, and ranking competing services.