Chronic absenteeism is a measure of how many students miss a defined number of school days for any reason--excused, unexcused, suspension. Many states define chronic absenteeism as the number and percentage of students missing 10 percent or more of their school days in a year. The purpose of this Brief is to provide information about chronic absenteeism and possible implications for students with disabilities when a state selects it as a measure of school quality or student success. It highlights both the benefits and potential risks in light of requirements in the Individuals with Disabilities Education Act (IDEA), Section 504 of the Rehabilitation Act of 1973 (Section 504), and the Americans with Disabilities Act (ADA). The Brief also suggests actions that states might consider taking to address chronic absences among students with disabilities at the state and local levels as they work to include this new measure in accountability systems. For purposes of this Brief, students with disabilities are those eligible for special education and related services under IDEA.