##### 



Exhibit 21

Subsidiaries

|                                      |  |             
|------------------------------------- |  | ------------
|Entity Name                           |  | Jurisdiction
|XO Communications, Inc. Subsidiaries: |  |             
|ITC                                   |  | Utah        
|LHP Equipment, Inc.                   |  | Delaware    
|XO Alabama, Inc.                      |  | Washington  
|XO Arizona, Inc.                      |  | Washington  
|XO California, Inc.                   |  | Washington  
|XO Colorado, LLC                      |  | Washington  
|XO Connecticut, Inc.                  |  | Washington  
|XO Delaware, Inc.                     |  | Washington  
|XO Domestic Holdings, Inc.            |  | Delaware    
|XO D.C., Inc.                         |  | Washington  
|XO Florida, Inc.                      |  | Washington  
|XO Georgia, Inc.                      |  | Washington  
|XO Hawaii, Inc.                       |  | Washington  
|XO Idaho, Inc.                        |  | Washington  
|XO Illinois, Inc.                     |  | Washington  
|XO Indiana, Inc.                      |  | Washington  
|XO Interactive, Inc.                  |  | Washington  
|XO International Holdings, Inc.       |  | Delaware    
|XO Kansas, Inc.                       |  | Washington  
|XO Kentucky, Inc.                     |  | Washington  
|XO LMDS Holdings No. 1, Inc.          |  | Nevada      
|XO Long Distance Services, Inc.       |  | Washington  
|XO Louisiana, Inc.                    |  | Washington  
|XO Maine, Inc.                        |  | Washington  
|XO Management Services, Inc.          |  | Washington  
|XO Maryland, LLC                      |  | Washington  
|XO Massachusetts, Inc.                |  | Washington  
|XO Michigan, Inc.                     |  | Washington  
|XO Minnesota, LLC                     |  | Washington  
|XO Mississippi, Inc.                  |  | Washington  
|XO Missouri, Inc.                     |  | Washington  
|XO Nevada Merger Sub., Inc.           |  | Delaware    
|XO New Hampshire, Inc.                |  | Washington  
|XO New Jersey, Inc.                   |  | Washington  
|XO New Mexico, Inc.                   |  | Washington  
|XO New York, Inc.                     |  | Washington  
|XO North Carolina, Inc.               |  | Washington  
|XO Ohio, Inc.                         |  | Washington  





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##### 



|                                                    |  |            
|--------------------------------------------------- |  | -----------
|XO One, Inc.                                        |  | Delaware   
|XO Oregon, Inc.                                     |  | Washington 
|XO Pennsylvania, Inc.                               |  | Washington 
|XO Rhode Island, Inc.                               |  | Washington 
|XO Services, Inc.                                   |  | Delaware   
|XO South Carolina, Inc.                             |  | Washington 
|XO Tennessee, Inc.                                  |  | Washington 
|XO Texas, Inc.                                      |  | Washington 
|XO Utah, Inc.                                       |  | Washington 
|XO Virginia, LLC                                    |  | Washington 
|XO Washington, Inc.                                 |  | Washington 
|XO West Virginia, Inc.                              |  | Washington 
|XO Wisconsin, Inc.                                  |  | Washington 
|40% Interest in Telecommunications of Nevada, L.L.C |  | Delaware   
|XO Domestic Holdings, Inc. Subsidiary:              |  |            
|XO Intercity Holdings No. 1, LLC                    |  | Washington 
|XO Mindshare, LLC                                   |  | Washington 
|XO International Holdings, Inc. Subsidiaries:       |  |            
|XO International, Inc.                              |  | Delaware   
|Nextlink Global ApS                                 |  | Denmark    
|XO Intercity Holdings No. 1, LLC Subsidiaries:      |  |            
|XO Data Services, LLC                               |  | Delaware   
|XO Intercity Holdings No. 2, LLC                    |  | Delaware   
|XO Long Distance Services, Inc. Subsidiary:         |  |            
|XO Long Distance Services (Virginia), LLC           |  | Washington 
|XO Management Services, Inc. Subsidiary:            |  |            
|XO Management Services Nevada, Inc.                 |  | Washington 
|XO Nevada Merger Sub., Inc.:                        |  |            
|50% Interest in Telecommunications of Nevada, L.L.C |  | Delaware   
|NEXTLINK Global ApS Subsidiaries:                   |  |            
|Nextlink Belgium, SRLP                              |  | Belgium    
|Nextlink France, SAS                                |  | France     
|Nextlink Deutschland, GMBH                          |  | Germany    
|Nextlink Netherlands, B.V                           |  | Netherlands