Exhibit 8.1



SIGNIFICANT SUBSIDIARIES



The following table sets forth our significant subsidiaries and investees accounted for using the equity method at December 31, 2003:



|                                                              |  |                              |  |                                           |  |                                                                                                                                                    
|------------------------------------------------------------- |  | ---------------------------- |  | ----------------------------------------- |  | ---------------------------------------------------------------------------------------------------------------------------------------------------
|Name of Company                                               |  | Jurisdiction ofEstablishment |  | Percentage ofOwnership andVoting Interest |  | Description                                                                                                                                        
|Alquiladora de Casas, S.A. de C.V.                            |  | Mexico                       |  | 100%                                      |  | Real estate company owning our facilities                                                                                                          
|Anuncios en Directorios, S.A. de C.V.                         |  | Mexico                       |  | 100%                                      |  | Producer of yellow pages directories                                                                                                               
|Compañía de Teléfonos y Bienes Raíces, S.A. de C.V.           |  | Mexico                       |  | 100%                                      |  | Real estate company owning our facilities                                                                                                          
|Consorcio Red Uno, S.A. de C.V.                               |  | Mexico                       |  | 100%                                      |  | Supplier of telecommunications network integration services and information systems                                                                
|Controladora de Servicios de Telecomunicaciones, S.A. de C.V. |  | Mexico                       |  | 100%                                      |  | Intermediate holding company                                                                                                                       
|Teléfonos del Noroeste, S.A. de C.V., or Telnor               |  | Mexico                       |  | 100%                                      |  | Fixed-line 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%                                      |  | Provider of connectivity and Internet access to Telmex and commercial customers                                                                    
|Financial Ventures LLC                                        |  | Delaware                     |  | 100%                                      |  | Company holding investments in publicly-traded equity securities and corporate bonds of technology and communications companies                    
|Technology and Internet, L.L.C.*                              |  | Delaware                     |  | 50%                                       |  | Company investing in e-commerce enterprises in the United States and Latin America                                                                 
|Telmex USA, L.L.C.                                            |  | Delaware                     |  | 100%                                      |  | Authorized reseller of long distance services and holder of FCC authorization to provide facility-based long distance services in the United States
|Telvista, Inc. (formerly, The Telvista Company)*              |  | Delaware                     |  | 45%                                       |  | Provider of telemarketing services in the United States and Mexico                                                                                 
|TM & MS, LLC*                                                 |  | Delaware                     |  | 50%                                       |  | Joint venture with Microsoft to operate an Internet portal                                                                                         

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|* | Investments accounted for using the equity method.
|- | --------------------------------------------------