The participation and performance of students in statewide accountability and assessment systems are measures of student and school success. These accountability systems theoretically reflect performance for all students, including students receiving special education. Yet few examine the participation and performance of students in special education by disability category, instead reporting on "special education" as a homogeneous population, when in fact it is not. Students with emotional disturbance (ED) demonstrate some of the most challenging academic and behavior problems and present low performances in school. The participation and performance of students with ED on a statewide accountability assessment in math were investigated in this article. Only 34% of students with ED participated and met at least minimum proficiency standards. Factors predictive of student participation and performance were identified through logistic regression. One primary finding is that instructional setting predicted participation, though not performance, and intuitively intelligence predicted both participation and performance. (Contains 1 table.)