GMSL’s Operations clients include:
| actogas | Distrigas | GasTerra | Nuon |
| AES Ballylumford | ECC | Gazprom M&T | Petronas Energy Trading |
| ATEL | EEX Power | GdF Great Britain | Quantum |
| Barclays Bank PLC | EGL AG | GDF Suez E&P Norge | Shell Gas Direct |
| Bayerngas Norge | Electrabel | Glencore | Societe Generale |
| BG Gas Services | Eneco Energie | Gunvor | Sojitz Energy |
| BNP Paribas | Enel Trade S.p.A | HEPGCO | Sonatrach |
| Cargill | Energy Logistics | Hess | Sorgenia |
| Chevron | ENOI S.p.A | ICE Clear Europe | TotalFinaElf Exploration |
| Citigroup | EOS | Ithaca Energy | Total Gas & Power |
| ConocoPhillips | EPEX Spot | Louis Dreyfus | Trafigura |
| Credit Suisse | ESB International | Macquarie Bank | Vattenfall |
| Delta Energy | Faroe Petroleum | Marathon | Viridian Energy |
| Deutsche Bank | Gas Natural | Mercuria | Vitol |
| Direct Energy | Gaselys | Morgan Stanley | VNG |
GMSL's Software Clients Include:
| Atel Trading | Edison | GE Plastics | RWE Midstream |
| Barclays Capital | EGL | Glencore | RWE Trading |
| BG International | EHW | Hepgco | Scottish & Southern |
| Bord Gais | Electrabel | Intergen | Scottish Power |
| BP | Energie Logistics | JP Morgan | Shell |
| Cargill International | ENI UK | Louis Dreyfus | Soteg |
| Centrica | ENI SpA | Macquarie Bank | SPE |
| Chevron North Sea | ENOI | Maersk | TAQA |
| ConocoPhillips | E.ON Energy Trading SE | Morgan Stanley | TFE Norge |
| Delta | EOS | Nexen | Total G&P |
| Direct Energie | Gas Natural | Norsk Hydro | UBS |
| Dong | Gaselys | Nuon | Vitol |
| EDFT | Gazprom M&T | RBS Sempra | ZMB |
