| Lockheed Martin Corporation | $624,871,725 |
| Weston Solutions, Inc. | $454,851,254 |
| Tetra Tech, Inc. | $447,989,087 |
| Environmental Quality Management, Inc. | $436,821,785 |
| SAIC, Inc. (formerly Science Applications International Corporation) | $345,856,548 |
| CH2M HILL Companies, Ltd. | $334,451,499 |
| Computer Sciences Corporation | $299,473,527 |
| Kaiser Group Holdings, Inc. | $294,341,087 |
| Earth Tech, Inc. | $268,900,892 |
| CDM Federal Programs Corporation | $230,772,989 |
| Eastern Research Group, Inc. | $184,407,816 |
| The Cadmus Group, Inc. | $176,234,814 |
| Battelle Memorial Institute | $157,472,758 |
| WRS Infrastructure & Environment Inc. | $146,614,107 |
| IT Corporation | $134,095,413 |
| Research Triangle Institute | $129,468,156 |
| Ecology and Environment, Inc. | $128,423,853 |
| Systems Research and Applications Corp. | $106,199,530 |
| URS Corporation | $103,551,881 |
| Booz Allen Hamilton Inc. | $101,598,433 |
| Black & Veatch Corporation | $96,039,673 |
| FEV Engine Technology, Inc, | $93,920,828 |
| CET Services, Inc.(formerly CET Environmental Services, Inc.) | $89,576,000 |
| Arctic Slope Regional Corporation | $86,556,660 |
| Newton Marasco Group Ltd. | $86,157,241 |
| Metcalf & Eddy Inc. | $82,207,906 |
| CMC Inc. | $82,109,377 |
| TechLaw, Inc. | $80,484,861 |
| ManTech International Corporation | $75,758,437 |
| Dynamac Corporation | $71,862,490 |
| Halliburton Company | $70,828,347 |
| Environmental Restoration, LLC | $66,578,465 |
| Transcontinental Enterprises Inc. | $65,565,522 |
| Shaw Environmental, Inc. | $63,786,745 |
| ARCADIS G&M (formerly ARCADIS Geraghty & Miller) | $62,899,026 |
| PRC Environmental Management, Inc. | $62,166,000 |
| Abt Associates Inc. | $60,578,914 |
| OAO Corporation | $56,939,069 |
| Southwest Research Institute | $49,015,058 |
| Foster Wheeler Environmental Corporation | $44,404,945 |
| Environmental Management Support Inc. | $41,351,688 |
| Computer Based Systems Inc. | $41,084,061 |
| Industrial Economics Inc. | $38,577,209 |
| KEMRON Environmental Services, Inc. | $38,575,118 |
| Westinghouse Remedial Services | $36,912,000 |
| Armstrong Data Services, Inc. | $36,262,957 |
| OHM Remediation Services | $36,114,390 |
| STG, Inc. | $34,862,477 |
| Gannett Fleming, Inc. | $34,180,158 |
| Versar, Inc. | $31,319,848 |
| Network Management, Inc. | $27,814,000 |
| EC/R Incorporated | $26,750,916 |
| DCT Inc. | $26,725,941 |
| Washington Metropolitan Area Transit Authority | $26,313,579 |
| International Business Machines Corporation | $26,207,274 |
| Sobran Inc. | $25,034,931 |