This paper seeks to shift debate from the question of whether charter schools are serving their "fair share" of students with disabilities to the more fruitful question of how finance and choice policies influence special education enrollment rates in charter schools. A school's incentive to enroll a student with disabilities depends on the difference between the additional revenues it receives versus the additional costs it incurs for serving that student. There are large interstate variations in special education enrollment rates in charter schools, and this correlates with state reimbursement rates for special education costs. Our analysis of intrastate patterns considers the effect of charter school size, age, for-profit management status, and autonomy from local school districts on their enrollment of students with disabilities. Evidence from Michigan indicates that special education enrollment rates are much more uniform across school districts than charter schools, and, among other things, the rate increases as charter schools become older. (Contains 6 tables, 2 figures and 6 footnotes.)