| Subsidiaries | | State of Incorporation or Organization |
| Bighorn Gas Gathering, L.L.C. (49.0%) | | Delaware |
| Bison Prairie Assurance, L.L.C. | | Oklahoma |
| Black Mesa Holdings, Inc. | | Delaware |
| Black Mesa Pipeline, Inc. | | Delaware |
| Black Mesa Pipeline Operations, L.L.C. | | Delaware |
| Black Mesa Technologies, Inc. | | Oklahoma |
| Border Midwestern Company | | Delaware |
| Chisholm Pipeline Company (50%) | | Delaware |
| Chisholm Pipeline Holdings, L.L.C. | | Delaware |
| Crestone Energy Ventures, L.L.C. | | Delaware |
| Crestone Gathering Services, L.L.C. | | Delaware |
| Crestone Powder River, L.L.C. | | Delaware |
| Crestone Wind River, L.L.C. | | Delaware |
| Fort Union Gas Gathering, L.L.C. (50%) | | Delaware |
| Guardian Pipeline, L.L.C. | | Delaware |
| Heartland Pipeline Company (general partnership) (50%) | | Texas |
| Lost Creek Gathering Company, L.L.C. (35%) | | Delaware |
| Mid Continent Market Center, L.L.C. | | Kansas |
| Midwestern Gas Transmission Company | | Delaware |
| Mont Belvieu I Fractionation Facility (joint venture) (80%) | | Texas |
| Northern Border Pipeline Company (general partnership) (50%) | | Texas |
| OkTex Pipeline Company, L.L.C. | | Delaware |
| ONEOK Arbuckle II Pipeline, L.L.C. | | Oklahoma |
| ONEOK Arbuckle North Pipeline, L.L.C. | | Delaware |
| ONEOK Arbuckle Pipeline, L.L.C. | | Delaware |
| ONEOK Bakken Pipeline, L.L.C. | | Delaware |
| ONEOK Bushton Processing, L.L.C. | | Delaware |
| ONEOK Elk Creek Pipeline, L.L.C. | | Oklahoma |
| ONEOK Energy Services Company, II | | Delaware |
| ONEOK Energy Services Company, L.P. | | Texas |
| ONEOK Energy Services Holdings, L.L.C. | | Oklahoma |
| ONEOK Field Services Company, L.L.C. | | Oklahoma |
| ONEOK Gas Storage Holdings, L.L.C. | | Delaware |
| ONEOK Gas Storage, L.L.C. | | Oklahoma |
| ONEOK Gas Transportation, L.L.C. | | Oklahoma |
| ONEOK Hydrocarbon GP, L.L.C. | | Delaware |
| ONEOK Hydrocarbon Holdings, L.L.C. | | Delaware |
| ONEOK Hydrocarbon Southwest, L.L.C. | | Delaware |
| ONEOK Hydrocarbon, L.L.C. | | Delaware |
| ONEOK Hydrocarbon, L.P. | | Delaware |
| ONEOK ILP GP, L.L.C. | | Delaware |
| ONEOK Leasing Company | | Delaware |
| ONEOK MB I, L.P. | | Delaware |
| Subsidiaries | | State of Incorporation or Organization |
| ONEOK Midstream Gas Supply, L.L.C. | | Oklahoma |
| ONEOK Mont Belvieu Properties, L.L.C. | | Delaware |
| ONEOK Mont Belvieu Storage Company, L.L.C. | | Delaware |
| ONEOK NGL Gathering, L.L.C. | | Delaware |
| ONEOK NGL Pipeline, L.L.C. | | Delaware |
| ONEOK North System, L.L.C. | | Delaware |
| ONEOK Northern Border Pipeline Company Holdings, L.L.C. | | Oklahoma |
| ONEOK Overland Pass Holdings, L.L.C. | | Oklahoma |
| ONEOK Parking Company, L.L.C. | | Delaware |
| ONEOK Partners GP, L.L.C. | | Delaware |
| ONEOK Partners Intermediate Limited Partnership | | Delaware |
| ONEOK Partners, L.P. | | Delaware |
| ONEOK Permian NGL Operating Company, L.L.C. | | Delaware |
| ONEOK Pipeline Holdings, L.L.C. | | Delaware |
| ONEOK Rockies Investments, L.L.C. | | Delaware |
| ONEOK Rockies Midstream, L.L.C. | | Delaware |
| ONEOK Services Company, L.L.C. | | Oklahoma |
| ONEOK Southeast Texas NGL Pipeline, L.L.C. | | Oklahoma |
| ONEOK Sterling III Pipeline, L.L.C. | | Oklahoma |
| ONEOK Texas Gas Storage, L.L.C. | | Texas |
| ONEOK Underground Storage Company, L.L.C. | | Kansas |
| ONEOK Unit Holdings, Inc. | | Delaware |
| ONEOK Ventures, L.L.C. | | Oklahoma |
| ONEOK Ventures Direct Investments, L.L.C. | | Oklahoma |
| ONEOK Ventures Fund Investments, L.L.C. | | Oklahoma |
| ONEOK VESCO Holdings, L.L.C. | | Delaware |
| ONEOK West Texas NGL Pipeline, L.L.C. | | Texas |
| ONEOK Western Trail Pipeline, L.L.C. | | Oklahoma |
| ONEOK WesTex Transmission, L.L.C. | | Delaware |
| Otter Merger Sub, LLC | | Delaware |
| Overland Pass Pipeline Company LLC (50%) | | Delaware |
| Roadrunner Gas Transmission Holdings, LLC (50%) | | Delaware |
| Roadrunner Gas Transmission, LLC (100% owned by Roadrunner Gas Transmission Holdings, LLC) | | Delaware |
| Saguaro Connector Pipeline, L.L.C. | | Delaware |
| Saguaro Connector Pipeline Holdings, L.L.C. | | Delaware |
| TXGC Pipelines, L.L.C. | | Delaware |
| TXGC Properties, L.L.C. | | Delaware |
| Venice Energy Services Company, L.L.C. (10.1765%) | | Delaware |
| Viking Gas Transmission Company | | Delaware |
