3Com,Bert Davenport, UA, ?
3Com S4,Tom Gentles, UA, ?
AudioTalk,
BroadSoft, Sam Hoffpauir/Brett Tate, UA, BroadWorks, basic
Catapult,
Cisco,
Columbia University, Jonathan Lennox, Proxy, sipd, Advanced
Columbia University, Xiaotao Wu, UA, sipc, Intermediate
Delta,
Dialogic, Jeff Mark, UA, Ojai, basic
Ericsson Utvecklings AB, Eric Turesson, proxy, goSIP, basic
Ericsson, Manuel Sanchez, Proxy, YASS, basic
Hewlett-Packard, Anders Kristensen, UA, Wiz, advanced
Hewlett-Packard, Anders Kristensen, proxy, HP SIP server, basic/intermediate
Hughes Software Systems, KS Binu, UA, ProtoQuick(TM) SIP Stack, basic
Indigo Software, Emmanuel Bertrand, SIP UA, Indigo User Agent, Intermediate
Indigo Software, Emmanuel Bertrand, SIP proxy, Indigo Proxy Server, Intermediate
Iwatsu Electric, Ken Tomitaka, UA, SIP KT, basic
Komodo Technology, Sam Sin, UA, Komodo SIP UA, basic
Lucent Technologies IN/Internet Software, Vijay K. Gurbani, proxy, iSIP, basic
MCI Worldcom ENSD, Steve Donovan, Proxy, NS/RS, Advanced
MCI Worldcom, Robert Sparks, UA, VoicePhone, advanced 
Mediatrix, Eric Tremblay, UA, APA, Advanced
Mediatrix, ?, Proxy, APA, ?
Microappliance, Shiv Haris, proxy, MCET, intermediate
Mitel, Jerry Yin
Motorola, Chen Jia, UA, SIP phone, basic
NetSpeak Co., Kevin Wang, proxy,NetSpeak SIP CMS,intermediate
Network Associate Inc.,  Miles Wu,  SIP protocol analyzer, all
Nortel Networks, Scott Orton, Proxy, Proxy, intermediate 
Nortel Networks, Scott Orton, UA, Sip Phone, advanced 
Nortel Networks, Scott Orton, UA, Sip Soft Client, advanced 
Nuera Communications Inc, Henry Lau, UA, NueraSIP API Library, Basic
Nuera, Derek Li, UA, NUERA-ID, basic
Nuera, Maroula Bratakos, UA, F200SIP, basic
Oz,
Pingtel, Dan Petrie, UA, Xpressa, advanced
SS8 Networks, Connie Blanchard, Proxy, SIP Proxy Server, intermediate
Siemens Communications Ltd, Thomas Zimprich, UA, SIP LITE-PHONE, basic
Startek Technologies, Dov Ben-Asher, UA, IPNess SIP, basic
Telogy,  Wing Man Kwok,  UA,  Golden Gateway,  Basic
Ubiquity Software Corporation Ltd, Matt Pickard, UA, Helmsman UA, intermediate
Ubiquity Software Corporation Ltd, Neil Deason, proxy, Helmsman SIP Server, advanced
VegaStream, Barry Desborough, UA, Vega50 IP Telephony Gateway, basic
Vovida Networks,Sunitha Kumar,UA,intermediate
dynamicsoft, Igor Slepchin, proxy, dynamicsoft Proxy, advanced
dynamicsoft, John Eichelsdorfer, UA, dynamicsoft Java UA, basic
dynamicsoft, Scott Happell, UA, dynamicsoft C++ UA, basic