Exhibit 21

List of Subsidiaries of Chiron Corporation

|Subsidiary                                                                     |                                                                                                              | Jurisdiction of Incorporation or
Organization                                                                                      
|------------------------------------------------------------------------------ | ------------------------------------------------------------------------------------------------------------ | -----------------------------------------------------------------------------------------------------------------------------------
|Cetus Generic Corporation                                                      |                                                                                                              | Delaware, USA                                                                                                                      
|Chiron B.V.                                                                    |                                                                                                              | The Netherlands                                                                                                                    
|                                                                               | Chiron Blood Testing B.V.                                                                                    |                                                                                                                                    
|Chiron B-1 Limited (formerly known as "Chiron IL-2 Technology (Bermuda) Ltd.") |                                                                                                              | Bermuda                                                                                                                            
|                                                                               | Chiron Blood Testing S.a.r.l.                                                                                |                                                                                                                                    
|                                                                               | Chiron Blood Testing (Bermuda) Ltd.                                                                          |                                                                                                                                    
|                                                                               |                                                                                                              | Chiron Healthcare Ireland Limited dba "Chiron Healthcare"* (formerly known as "Chiron Blood Testing Distributor (Bermuda) Limited")
|                                                                               |                                                                                                              | Chiron Blood Testing Pty Ltd                                                                                                       
|                                                                               | Chiron France S.a.r.l.                                                                                       |                                                                                                                                    
|                                                                               | Chiron U.K. Ltd.                                                                                             |                                                                                                                                    
|                                                                               | Chiron Iberia S.L.                                                                                           |                                                                                                                                    
|                                                                               | Chiron Corporation Limited (formerly known as "PathoGenesis, Ltd.")                                          |                                                                                                                                    
|                                                                               | Chiron Canada ULC* (formerly known as "Chiron Canada Limited"; formerly known as "PathoGenesis Canada, Ltd") |                                                                                                                                    
|                                                                               | PathoGenesis PortugalProdutos Farmacêuticos, Sociedade Unipessoal Lda.                                      |                                                                                                                                    
|Appold Consultadoria E Services Lda                                            |                                                                                                              | Portugal                                                                                                                           
|Chiron Investment Company Spain, S.L.                                          |                                                                                                              | Spain                                                                                                                              
|Chiron GmbH                                                                    |                                                                                                              | Germany                                                                                                                            
|Chiron Partners, Inc.                                                          |                                                                                                              | California, USA                                                                                                                    
|Chiron Italia S.r.l                                                            |                                                                                                              | Italy                                                                                                                              
|Chiron Alpha Corporation                                                       |                                                                                                              | California, USA                                                                                                                    
|Chiron/Cephalon JV                                                             |                                                                                                              | Delaware, USA                                                                                                                      
|Chiron Properties, Inc.                                                        |                                                                                                              | California, USA                                                                                                                    
|Chiron Delta Corporation                                                       |                                                                                                              | Delaware, USA                                                                                                                      
|Chiron Investment Corporation                                                  |                                                                                                              | California, USA                                                                                                                    
|                                                                               |                                                                                                              |                                                                                                                                    
|*    Name changes effective January 2002.                                      |                                                                                                              |                                                                                                                                    
|                                                                               |                                                                                                              |                                                                                                                                    

---

|Chiron Overseas Holding Co.                                                                         |                                            | Nevada, USA        
|--------------------------------------------------------------------------------------------------- | ------------------------------------------ | -------------------
|                                                                                                    | Chiron B-2 Limited                         |                    
|PathoGenesis Corporation                                                                            |                                            | Delaware, USA      
|                                                                                                    | PathoGenesis France SARL                   |                    
|                                                                                                    | PathoGenesis BV                            |                    
|                                                                                                    | PulmoPharmGmbH (19.9%)                     |                    
|Manon Acquisition Corp.                                                                             |                                            | Delaware           
|Chiron Redevelopment Corp. & Co. KG                                                                 |                                            | Germany            
|31. Corsa Verwaltungsgesellschaft mbH                                                               |                                            | Germany            
|                                                                                                    | Chiron Behring GmbH & Co                   |                    
|                                                                                                    | Chiron Behring Verwaltungsgesellschaft mbH |                    
|Chiron S.p.A.                                                                                       |                                            | Italy              
|                                                                                                    | Istituto Vaccinogeno Pozzi S.p.A.          |                    
|                                                                                                    | Chiron Funding LLC (0.01%)                 |                    
|Chiron Technologies Pty. Ltd.                                                                       |                                            | Australia          
|Chiron Mimotopes U.S.                                                                               |                                            | California, USA    
|Chiron Redevelopment Corporation                                                                    |                                            | Missouri, USA      
|Chiron Foreign Sales Corporation                                                                    |                                            | U.S. Virgin Islands
|Chiron Funding Corporation                                                                          |                                            | Delaware, USA      
|Biocent Insurance Company, Inc.                                                                     |                                            | Hawaii, USA        
|Chiron Vision Canada, Inc.                                                                          |                                            | Canada             
|Chiron Behring Vaccines Private Limited (51%) (formerly known as "Chiron Behring Vaccines Limited") |                                            | India              
|Chiron Limited (50%)                                                                                |                                            | Hong Kong          

---

QuickLinks