Exhibit 8.1

Significant Subsidiaries and Investees

The following table sets forth our significant subsidiaries and investees accounted
for using the equity method at December 31, 2007:



|                                                    |  |                             |  |                                         |   |  |                                                                                                                                                                                                                                                     
|--------------------------------------------------- |  | --------------------------- |  | --------------------------------------- | - |  | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
|Name of Company                                     |  | Jurisdictionofestablishment |  | Percentageofownershipand votinginterest |   |  | Description                                                                                                                                                                                                                                         
|Subsidiaries                                        |  |                             |  |                                         |   |  |                                                                                                                                                                                                                                                     
|Integración de Servicios TMX, S.A. de C.V.          |  | Mexico                      |  | 100.0                                   | % |  | Intermediate holding company                                                                                                                                                                                                                        
|                                                    |  |                             | 
|Alquiladora de Casas, S.A. de C.V.                  |  | Mexico                      |  | 100.0                                   | % |  | Real estate company owning our facilities                                                                                                                                                                                                           
|                                                    |  |                             | 
|Compañía de Teléfonos y Bienes Raíces, S.A. de C.V. |  | Mexico                      |  | 100.0                                   | % |  | Real estate company owning our facilities                                                                                                                                                                                                           
|                                                    |  |                             | 
|Consorcio Red Uno, S.A. de C.V.                     |  | Mexico                      |  | 100.0                                   | % |  | Supplier of telecommunications network integration services and information systems                                                                                                                                                                 
|                                                    |  |                             | 
|Teléfonos del Noroeste, S.A. de C.V.                |  | Mexico                      |  | 100.0                                   | % |  | Fixed-line public network concessionaire for the state of Baja California Norte and the San Luis Rio Colorado region of the state of Sonora                                                                                                         
|                                                    |  |                             | 
|Uninet, S.A. de C.V.                                |  | Mexico                      |  | 100.0                                   | % |  | Provider of corporate networks and Internet access services to Telmex and corporate customers                                                                                                                                                       
|                                                    |  |                             | 
|Telmex USA, L.L.C.                                  |  | Delaware                    |  | 100.0                                   | % |  | Authorized long distance service re-seller, telephone card sales, receipt of payments for lines in Mexico (installation expenses and monthly rental) and authorized by the FCC to provide
facility-based long distance services in the United States
|Affiliated companies                                |  |                             |  |                                         |   |  |                                                                                                                                                                                                                                                     
|Grupo Telvista S.A. de C.V.                         |  | Mexico                      |  | 45.0                                    | % |  | Provider of telemarketing services in the United States and Mexico                                                                                                                                                                                  
|                                                    |  |                             | 
|2Wire, Inc.                                         |  | California                  |  | 13.0                                    | % |  | Broadband network equipment and service provider for residential and small-business customers