The purpose of this project is to identify how entities who have adopted the Common Core State Standards (CCSS) are addressing this option to add content to the standards. This report describes the policy decisions of adopters on the "15 percent question" as well as reports on and lists any such additional standards they have identified thus far. McREL discussed the adoption with representatives of six adopting state departments of education in the Central Region over the last several months and learned that how others have addressed this option is of interest. As additional states consider the question of whether they should add state material to the Common Core State Standards, this report may aid their considerations. Lists of state standards documents reviewed and sources consulted are included. Appended are: (1) Profiles of the 15 Percent Decision for States who Have Chosen to Add Content; (2) Math Content Added by States to the CCSS; and (3) English Language Arts Content Added by States. (Contains 3 figures and 1 footnote. )