Holding(s) in Company

Cambridge Antibody Tech Group PLC
18 May 2006

                   NOTIFICATION OF MAJOR INTERESTS IN SHARES



1. Name of company



Cambridge Antibody Technology Group plc



2. Name of shareholder having a major interest



Wellington Management Company LLP



3. Please state whether notification indicates that it is in respect of holding
of the shareholder named in 2 above or in respect of a non-beneficial interest
or in the case of an individual holder if it is a holding of that person's
spouse or children under the age of 18



Non beneficial



4. Name of the registered holder(s) and, if more than one holder, the number of
shares held by each of them



Investment Advisor. Names of separate accounts not disclosed. The shares are
registered in the name of the Accounts of the Accounts Custodians or nominees
according to their respective holdings.



5. Number of shares / amount of stock acquired



not disclosed



6. Percentage of issued class



N/A



7. Number of shares / amount of stock disposed



not disclosed



8. Percentage of issued class



N/A



9. Class of security



ordinary 10 pence shares



10. Date of transaction



not disclosed

11. Date company informed



18 May 2006



12. Total holding following this notification



1,789,421



13. Total percentage holding of issued class following this notification



3.363%



14. Any additional information



The Accounts do not act as a group nor do they act in concert with respect to
the interests in shares.



15. Name of contact and telephone number for queries



Justin Hoskins 01223 898589



16. Name and signature of authorised company official responsible for making
this notification



Justin Hoskins Company Secretary



Date of notification



18 May 2006



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