For immediate release: July 20, 2006

MDA Books Contract Extension For Continued Support Of Mobile Servicing System For The International Space Station

Richmond, B.C. - MacDonald, Dettwiler and Associates Ltd. (TSX: MDA), a provider of essential information solutions, announced today that it has signed a C$32.8 million contract extension with the Canadian Space Agency to provide logistics, sustaining engineering, and enhancements for the Mobile Servicing System. The Mobile Servicing System was designed and built by MDA under contract to the Canadian Space Agency, as part of Canada's contribution to the International Space Station.

The Mobile Servicing System plays a central role in the construction and maintenance of the Space Station and is comprised of a mobile base station, the Canadarm2, and the soon to be launched advanced servicing manipulator known as "Dextre." This award extends through May 2008 MDA's existing contract to maintain these Canadian supplied on-orbit assets, to carry out mission analysis, and to implement software enhancements.

Enhancements to the Mobile Servicing System made under this contract will facilitate the capture of unmanned vehicles such as Japan's HTV visiting the International Space Station with supplies and construction materials.

This contract further extends Canada's leadership role in supporting manned and unmanned space missions with advanced on-orbit servicing solutions, and it positions MDA to continue as a leader in this field well beyond the end of the Shuttle era.

About MDA

MDA provides advanced information solutions that capture and process vast amounts of data, produce essential information, and improve the decision making and operational performance of business and government organizations worldwide.

Focused on markets and customers with strong repeat business potential, MDA delivers a broad spectrum of earth and space based information solutions, ranging from complex operational systems, to tailored information services, to electronic information products.

MDA employs more than 3,000 people in locations across the United States, the United Kingdom, and Canada. The Company's common shares trade on the Toronto Stock Exchange under the symbol. TSX:MDA.

Related Websites:
www.mdacorporation.com
www.space.gc.ca

Forward-Looking Statement
This release contains forward-looking statements and information, which reflect the current view of MacDonald, Dettwiler and Associates Ltd. with respect to future events and financial performance. Any such forward-looking statements are subject to risks and uncertainties and MDA's actual results of operations could differ materially from historical results or current expectations. Additional information on these and other potential factors that could affect MDA's financial results are detailed in documents filed from time to time with the applicable Canadian securities regulatory authorities.

The Toronto Stock Exchange has neither approved nor disapproved the form or content of this release.