Charter schools embody the theoretical potential to promote integration since they can draw students from across district boundaries that often reflect segregated residential patterns. While a number of studies have examined overall racial composition of charter schools, virtually no attention has been paid to how charter school enrollment patterns may have changed over time--a key for understanding the potential of these schools to exacerbate or ameliorate student sorting. We examine questions of school mix by comparing the integration indices of charter schools over time. The analysis indicates that integration in charter schools has improved slightly in the majority of states but that in several states charter schools are seeing increased segregation. (Contains 8 notes and 2 tables.)