EXHIBIT 21



SIGNIFICANT SUBSIDIARIES OF CAREMARK RX, INC. (1)



|                                   |  |                                                        |  |                                                            
|---------------------------------- |  | ------------------------------------------------------ |  | -----------------------------------------------------------
|Legal Name                         |  | State or Jurisdiction of Incorporation
or Organization |  | Also Doing Business As                                     
|                                   |  |                                                       
|Caremark International Inc.        |  | Delaware                                               |  | N/A                                                        
|                                   |  |                                                       
|Caremark Inc.                      |  | California                                             |  | Caremark Prescription ServicesCaremark Therapeutic Services
|                                   |  |                                                       
|CaremarkPCS                        |  | Delaware                                               |  | AdvancePCS Caremark                                        
|                                   |  |                                                       
|AdvancePCS Holding Corporation     |  | Delaware                                               |  | N/A                                                        
|                                   |  |                                                       
|CaremarkPCS Health Systems, L.L.C. |  | Delaware                                               |  | N/A                                                        
|                                   |  |                                                       
|ADVP Consolidation, L.L.C.         |  | Delaware                                               |  | N/A                                                        
|                                   |  |                                                       
|CaremarkPCS Health, L.P.           |  | Delaware                                               |  | Caremark                                                   
|                                   |  |                                                       
|SilverScript, Inc.                 |  | Delaware                                               |  | N/A                                                        
|                                   |  |                                                       
|SilverScript Insurance Company     |  | Tennessee                                              |  | N/A                                                        

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|(1) | Certain subsidiaries of Caremark Rx, Inc. have been omitted from the above listing pursuant to Item 601(b)(21)(ii) of Regulation S-K. These subsidiaries would, if considered in
the aggregate as a single subsidiary, not constitute a significant subsidiary as this term is defined by the SEC.
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