Exhibit 21.1



|                                                |  |                      
|----------------------------------------------- |  | ---------------------
|Subsidiary                                      |  | State of Organization
|101 Carnegie Center Associates                  |  | New Jersey           
|17M Acquisition Subsidiary LLC                  |  | Delaware             
|17M Associates                                  |  | District of Columbia 
|191 Spring Street Trust                         |  | Massachusetts        
|206 Associates Limited Partnership              |  | New Jersey           
|210 Associates Limited Partnership              |  | New Jersey           
|211 Associates Limited Partnership              |  | New Jersey           
|30 Shattuck Road LLC                            |  | Delaware             
|40-46 Harvard Street Trust                      |  | Massachusetts        
|46th & Eighth Associates, LLC                   |  | Delaware             
|738 Eighth Avenue LLC                           |  | Delaware             
|90 Church Street Limited Partnership            |  | Delaware             
|91 Hartwell Avenue Trust                        |  | Massachusetts        
|92 Hayden Avenue Trust                          |  | Massachusetts        
|Big Apple Associates Limited Partnership        |  | Delaware             
|Billerica Road LLC                              |  | Delaware             
|Billerica Road Member LLC                       |  | Delaware             
|Boston Properties LLC                           |  | Delaware             
|Boston Properties Management, Inc.              |  | Delaware             
|Boston Properties Office Value-Added Fund, L.P. |  | Delaware             
|Boston Properties TRS, Inc.                     |  | Delaware             
|BP 111 Huntington Ave LLC                       |  | Delaware             
|BP 1330 Connecticut Avenue LLC                  |  | Delaware             
|BP 1333 New Hampshire Avenue LLC                |  | Delaware             
|BP 140 Kendrick Street LLC                      |  | Delaware             
|BP 140 Kendrick Street Property LLC             |  | Delaware             
|BP 20 F Street Limited Partnership              |  | Delaware             
|BP 201 Spring Street LLC                        |  | Delaware             
|BP 280 Park Avenue LLC                          |  | Delaware             
|BP 280 Park Avenue Manager Corp.                |  | Delaware             
|BP 280 Park Avenue Mezzanine LLC                |  | Delaware             
|BP 399 Park Avenue LLC                          |  | Delaware             
|BP 8th Avenue Associates LLC                    |  | Delaware             
|BP Almaden Associates LLC                       |  | Delaware             
|BP Belvidere LLC                                |  | Delaware             
|BP Crane Meadow, L.L.C.                         |  | Delaware             
|BP EC West LLC                                  |  | Delaware             
|BP EC1 Holdings LLC                             |  | Delaware             
|BP EC2 Holdings LLC                             |  | Delaware             
|BP EC3 Holdings LLC                             |  | Delaware             
|BP EC4 Holdings LLC                             |  | Delaware             
|BP Fan Pier Development LLC                     |  | Delaware             
|BP Fourth Avenue, L.L.C.                        |  | Delaware             
|BP Gateway Center LLC                           |  | Delaware             
|BP Hotel LLC                                    |  | Delaware             
|BP II LLC                                       |  | Delaware             
|BP III LLC                                      |  | Delaware             
|BP Lex LLC                                      |  | Delaware             



---

|                                                     |  |                      
|---------------------------------------------------- |  | ---------------------
|Subsidiary                                           |  | State of Organization
|BP Management, L.P.                                  |  | Delaware             
|BP New Dominion Technology Office Park II, LLC       |  | Delaware             
|BP Office Fund REIT, Inc.                            |  | Maryland             
|BP Office Value-Added LLC                            |  | Delaware             
|BP OFR LLC                                           |  | Delaware             
|BP Prospect Place LLC                                |  | Delaware             
|BP Prucenter Acquisition LLC                         |  | Delaware             
|BP Prucenter Development LLC                         |  | Delaware             
|BP Prucenter Fairfield LLC                           |  | Delaware             
|BP Realty New Jersey LLC                             |  | New Jersey           
|BP Reston Eastgate LLC                               |  | Delaware             
|BP Reston Streets LLC                                |  | Delaware             
|BP Seven Cambridge Center LLC                        |  | Delaware             
|BP Supermarket LLC                                   |  | Delaware             
|BP Times Square Tower Mezzanine LLC                  |  | Delaware             
|BP Weston Quarry LLC                                 |  | Delaware             
|BP/CG Member I LLC                                   |  | Delaware             
|BP/CG Member II LLC                                  |  | Delaware             
|BP/CG Member III LLC                                 |  | Delaware             
|BP/CGCenter Acquisition Co. LLC                      |  | Delaware             
|BP/CGCenter I LLC                                    |  | Delaware             
|BP/CGCenter II LLC                                   |  | Delaware             
|BP/CGCenter MM LLC                                   |  | Delaware             
|BP/CGCenter MM2 LLC                                  |  | Delaware             
|BP/CRF 265 Franklin Street Holdings LLC              |  | Delaware             
|BP/CRF 265 Franklin Street LLC                       |  | Delaware             
|BP/CRF 265 Franklin Street Manager Corp.             |  | Delaware             
|BP/CRF 265 Franklin Street Mezzanine LLC             |  | Delaware             
|BP/CRF 901 New York Avenue LLC                       |  | Delaware             
|BP/DC Properties, Inc.                               |  | Maryland             
|BP/DC REIT LLC                                       |  | Delaware             
|Cambridge Center North Trust                         |  | Massachusetts        
|Cambridge Center West Associates Limited Partnership |  | Massachusetts        
|Cambridge Center West Garage LLC                     |  | Delaware             
|Cambridge Center West Trust                          |  | Massachusetts        
|Carnegie 214 Associates Limited Partnership          |  | New Jersey           
|Carnegie 504 Associates                              |  | New Jersey           
|Carnegie 506 Associates                              |  | New Jersey           
|Carnegie 508 Associates                              |  | New Jersey           
|Carnegie 510 Associates, L.L.C.                      |  | Delaware             
|Carnegie Center Associates                           |  | New Jersey           
|CRF Met Square LLC                                   |  | Delaware             
|Decoverly Five Limited Partnership                   |  | Maryland             
|Decoverly Four Limited Partnership                   |  | Maryland             
|Democracy Associates Limited Partnership             |  | Maryland             
|Democracy Financing, LLC                             |  | Delaware             
|Discovery Square, L.L.C.                             |  | Delaware             
|Downtown Boston Properties Trust                     |  | Massachusetts        
|East Pratt Street Associates Limited Partnership     |  | Maryland             
|Elandzee Trust                                       |  | Massachusetts        



---

|                                                             |  |                      
|------------------------------------------------------------ |  | ---------------------
|Subsidiary                                                   |  | State of Organization
|Eleven Cambridge Center Trust                                |  | Massachusetts        
|Embarcadero Center Associates                                |  | California           
|Embarcadero Center, Inc.                                     |  | California           
|Four Embarcadero Center Venture                              |  | California           
|Fourteen Cambridge Center Trust                              |  | Massachusetts        
|Gateway Center LLC                                           |  | Delaware             
|HarborPlace Boston LLC                                       |  | Delaware             
|Hayden Office Trust                                          |  | Massachusetts        
|IXP, Inc.                                                    |  | Vermont              
|Jones Road Development Associates LLC                        |  | Delaware             
|KEG I Associates, LLC                                        |  | Delaware             
|Lexreal Associates Limited Partnership                       |  | New York             
|LKE BP Fourth Avenue Limited Partnership                     |  | Massachusetts        
|Mall Road Trust                                              |  | Massachusetts        
|Market Square North Associates Limited Partnership           |  | Delaware             
|MBZ-Lex Trust                                                |  | Massachusetts        
|MGA Virginia 85-1 Limited Partnership                        |  | Virginia             
|MGA Virginia 86-1 Limited Partnership                        |  | Virginia             
|MGA Virginia 86-2 Limited Partnership                        |  | Virginia             
|Montgomery Village Avenue Joint Venture Limited Partnership  |  | Maryland             
|New Dominion Technology Corp.                                |  | Delaware             
|New Dominion Technology Park II LLC                          |  | Delaware             
|New Dominion Technology Park LLC                             |  | Delaware             
|No. 1 Times Square Development LLC                           |  | Delaware             
|No. 5 Times Square Development LLC                           |  | Delaware             
|Ocean View Development Company Limited Partnership           |  | District of Columbia 
|One Cambridge Center Trust                                   |  | Massachusetts        
|One Embarcadero Center Venture                               |  | California           
|One Freedom Square, L.L.C.                                   |  | Delaware             
|Pratt Street Financing, LLC                                  |  | Delaware             
|Princeton 202 Associates Limited Partnership                 |  | New Jersey           
|Princeton Childcare Associates Limited Partnership           |  | New Jersey           
|Reston Corporate Center Limited Partnership                  |  | Virginia             
|Reston Town Center Office Park Phase One Limited Partnership |  | Virginia             
|Reston VA 939, L.L.C.                                        |  | Delaware             
|School Street Associates Limited Partnership                 |  | District of Columbia 
|SCV Partners                                                 |  | New Jersey           
|Square 407 Limited Partnership                               |  | District of Columbia 
|Stony Brook Associates LLC                                   |  | Delaware             
|Ten Cambridge Center Trust                                   |  | Massachusetts        
|The Double B Partnership                                     |  | Massachusetts        
|The Double B Trust                                           |  | Massachusetts        
|The Metropolitan Square Associates LLC                       |  | District of Columbia 
|Three Cambridge Center Trust                                 |  | Massachusetts        
|Three Embarcadero Center Venture                             |  | California           
|Times Square Tower Associates LLC                            |  | Delaware             
|Tower Oaks Financing LLC                                     |  | Delaware             
|Tracer Lane Trust II                                         |  | Massachusetts        
|Two Cambridge Center Trust                                   |  | Massachusetts        
|Two Freedom Square, L.L.C.                                   |  | Delaware             



---

|                                                   |  |                      
|-------------------------------------------------- |  | ---------------------
|Subsidiary                                         |  | State of Organization
|Washingtonian North Associates Limited Partnership |  | Maryland             
|Wisconsin Place Office LLC                         |  | Delaware             
|Wisconsin Place Office Manager LLC                 |  | Delaware             
|Wisconsin Place Retail LLC                         |  | Delaware             
|Worldgate Member LLC                               |  | Delaware             
|Worldgate Plaza LLC                                |  | Delaware             
|WP Borrower LLC                                    |  | Delaware             
|WP Owner Trust                                     |  | Delaware             
|WP Trust                                           |  | Massachusetts        
|WP Project Developer LLC                           |  | Delaware             
|WP Project Developer Trust                         |  | Delaware             
|Zee Bee Trust II                                   |  | Massachusetts        
|Zee Em Trust II                                    |  | Massachusetts