This paper presents the assessment and item specifications for the National Assessment of Educational Progress (NAEP) 2009 mathematics assessment. "Chapter Two" contains descriptions of the five major content areas of mathematics (Number Properties and Operations, Measurement, Geometry, Data Analysis, Statistics, and Probability, and Algebra), as well as the specific objectives for grades 4, 8 and 12 that will be assessed. Further specifications are added to some objectives to clarify the intent for item writers. Each NAEP mathematics test item is designed to measure a specific level of thinking, called the mathematical complexity of the item. "Chapter Three" describes the three levels and offers examples of each. "Chapter Four" describes considerations for good item writing, with multiple examples of how each characteristic of an item might be met. The chapter also contains a description of the item tryout and review process. Each form of the NAEP mathematics assessment must be balanced according to a number of different factors, including content, level of complexity, and format. In "Chapter Five" the guidelines for balancing each factor are described. The chapter also addresses other issues of design, such as sampling, use of calculators, tools and manipulatives, and accessibility for all students. Three appendices are included: (1) NAEP Mathematics Achievement Level Descriptions; (2) NAEP Item Development and Review Policy Statement; and (3) NAEP Mathematics Project Staff and Committees. (Contains 8 footnotes.) [This report is a companion to Mathematics Framework for the 2009 National Assessment of Educational Progress. For the main report, see ED502928.]