EXHIBIT 21

SUBSIDIARIES OF THE REGISTRANT

|Name                                             |  | Direct Parent(s)                                                          |  | Ownership |    | Jurisdiction of
Incorporation
|------------------------------------------------ |  | ------------------------------------------------------------------------- |  | --------- | -- | -----------------------------
|BioMarin/Genzyme LLC                             |  | Genzyme Corporation                                                       |  | 50        | %  | Delaware                     
|Genzyme Europe B.V.                              |  | Imtix SangStat (Switzerland) GmbH                                         |  | 100       | %  | The Netherlands              
|Genzyme Flanders BVBA                            |  | Genzyme International Holdings Limited
SangStat Luxembourg S.à.r.l.       |  | 99.9
0.1  | %% | Belgium                      
|Genzyme GmbH                                     |  | Genzyme Europe B.V.                                                       |  | 100       | %  | Germany                      
|Genzyme International
Holdings Limited           |  | SangStat Luxembourg S.à.r.l.                                              |  | 100       | %  | Republic of Ireland          
|Genzyme Ireland Limited                          |  | Genzyme International Holdings Limited                                    |  | 100       | %  | Republic of Ireland          
|Genzyme Limited                                  |  | Genzyme Corporation                                                       |  | 100       | %  | United Kingdom               
|Genzyme Securities
Corporation                   |  | Genzyme Corporation                                                       |  | 100       | %  | Massachusetts                
|Genzyme Pharmaceuticals
AG                       |  | SangStat Luxembourg S.à.r.l.                                              |  | 100       | %  | Switzerland                  
|Genzyme Polyclonals S.A.S.                       |  | SangStat Medical, LLC
SangStat Atlantique S.A.S.                          |  | 1
99      | %% | France                       
|Genzyme Therapeutic
Products Limited
Partnership |  | Genzyme Therapeutic Products Corporation
Genzyme Therapeutic Products LLC |  | 1
99      | %% | Massachusetts                
|Genzyme Therapeutic
Products Corporation         |  | Genzyme Corporation                                                       |  | 100       | %  | Massachusetts                
|Genzyme Therapeutic
Products LLC                 |  | Genzyme Corporation                                                       |  | 100       | %  | Delaware                     
|Imtix SangStat
(Switzerland) GmbH                |  | SangStat Luxembourg S.à.r.l.                                              |  | 100       | %  | Switzerland                  
|SangStat Atlantique S.A.S.                       |  | SangStat Medical, LLC                                                     |  | 100       | %  | France                       
|SangStat Luxembourg
S.à.r.l.                     |  | Genzyme Luxembourg S.à.r.l.                                               |  | 100       | %  | Luxembourg                   

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