HOUSTON, TEXAS - June 15, 2006 - Enterprise Systems Corporation announced today that Marathon Oil Company has selected Enterprise Systems to perform an extensive IP Telephony deployment at its facilities in Equatorial Guinea. The scope of work will include network assessment, upgrades to three Meridian 1/CS1000 systems and IP trunking to network all three sites via H.323 Gateways. Enterprise Systems was chosen by Marathon after extensive evaluation of different Nortel Partners. A proven track record, extensive off-shore experience and reputation contributed to the decision.