Exhibit 8.1

List of Subsidiaries of the Registrant

|Company                                                     |  | Ownership(1) |  | Location          
|----------------------------------------------------------- |  | ------------ |  | ------------------
|Serono International S.A.                                   |  | 100%         |  | Switzerland       
|Ares Trading S.A.                                           |  | 100%         |  | Switzerland       
|Laboratoires Serono S.A.                                    |  | 100%         |  | Switzerland       
|Serono Argentina S.A.                                       |  | 100%         |  | Argentina         
|Serono Australia Pty Ltd                                    |  | 100%         |  | Australia         
|Serono Austria GmbH.                                        |  | 100%         |  | Austria           
|Serono Produtos Farmaceuticos Ltda                          |  | 100%         |  | Brazil            
|Serono Canada, Inc.                                         |  | 100%         |  | Canada            
|Serono International Services Limited.                      |  | 100%         |  | Cayman Islands    
|Serono 92 Limited                                           |  | 100%         |  | Cayman Islands    
|Serono de Colombia S.A.                                     |  | 100%         |  | Colombia          
|Applied Research Systems ARS Holding N.V.                   |  | 100%         |  | Curaçao           
|Serono Pharma Services, s.r.o.                              |  | 100%         |  | Czech Republic    
|Serono Genetics Institute S.A.                              |  | 100%         |  | France            
|Serono France S.A.                                          |  | 100%         |  | France            
|Serono France Holding S.A.                                  |  | 100%         |  | France            
|Serono GmbH                                                 |  | 100%         |  | Germany           
|Serono Hellas A.E.                                          |  | 100%         |  | Greece            
|Serono Hong Kong Ltd.                                       |  | 100%         |  | Hong Kong         
|Serono Israel Ltd                                           |  | 100%         |  | Israel            
|Horizon North SA                                            |  | 100%         |  | Switzerland       
|Horizon South SA                                            |  | 100%         |  | Switzerland       
|InterPharm Laboratories Ltd.                                |  | 100%         |  | Israel            
|Inter-Lab Ltd.                                              |  | 100%         |  | Israel            
|InterPharm Industries (1991) Ltd                            |  | 100%         |  | Israel            
|Industria Farmaceutica Serono S.p.A.                        |  | 96.67%       |  | Italy             
|Istituto di Ricerche Biomediche "Antoine Marxer" RBM S.p.A. |  | 97.97%       |  | Italy             
|Lockshield lLtd                                             |  | 100%         |  | Bermuda           
|Serono Japan Co. Ltd.                                       |  | 100%         |  | Japan             
|Serono Korea Co. Ltd.                                       |  | 100%         |  | Korea             
|Serono de Mexico S.A. de C.V.                               |  | 100%         |  | Mexico            
|Serono Produtos Farmaceuticos Lda                           |  | 100%         |  | Portugal          
|Serono Singapore Pte Ltd                                    |  | 100%         |  | Singapore         
|Serono South Africa (Pty) Ltd                               |  | 100%         |  | South Africa      
|Serono España S.A.                                          |  | 100%         |  | Spain             
|Serono Nordic AB.                                           |  | 100%         |  | Sweden            
|Serono (Thailand) Co., Ltd.                                 |  | 100%         |  | Thailand          
|Istituto Farmacologico Serono Nederland B.V.                |  | 100%         |  | The Netherlands   
|Serono B.V.                                                 |  | 100%         |  | The Netherlands   
|Serono Tri Holdings B.V.                                    |  | 100%         |  | The Netherlands   
|Serono Benelux B.V.                                         |  | 100%         |  | The Netherlands   
|Serono Ilaç Pazarlama ve Ticaret A.S.                       |  | 100%         |  | Turkey            
|Serono Ltd.                                                 |  | 100%         |  | United Kingdom    
|Serono Europe Ltd                                           |  | 100%         |  | United Kingdom    
|Serono Holding, Inc.                                        |  | 100%         |  | Massachusetts, USA
|Serono, Inc.                                                |  | 100%         |  | Delaware, USA     
|Serono Technologies SA                                      |  | 100%         |  | Switzerland       
|Serono Reproductive Biology Institute, Inc.                 |  | 100%         |  | Massachusetts, USA
|Ares Trading Uruguay S.A.                                   |  | 100%         |  | Uruguay           
|Serono de Venezuela S.A.                                    |  | 100%         |  | Venezuela         
|Serono d.o.o.                                               |  | 100%         |  | Croatia           

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