H.R.296: To specify that the 100 most populous urban areas of the United States, as determined by the Secretary of Homeland Security, shall be eligible for grants under the Urban Area Security Initiative of the Department of Homeland Security, and for other purposes.

Urban Area Security Initiative Improvement Act of 2007 - Makes each of the 100 most populous U.S. urban areas eligible for a grant under the Urban Area Security Initiative. Directs the Secretary of Homeland Security to award such grants after considering a study of how the variation in the output of models used for such awards can be apportioned to different sources of variation.