High School graduation rates are key indicators of accountability for high schools and school districts in Oregon. Beginning with the 2008-09 school year, the Oregon Department of Education (ODE) implemented the cohort method of calculating graduation rates. The cohort method identifies the year the student entered high school for the first time (known as the high school entry year, or cohort year) and uses longitudinal student data to determine the student's outcome after four years. An extended rate, allowing one additional year for completion, is also tracked and reported as the 5-year Cohort Graduation Rates. These reports include other outcome categories for students in the cohort, in addition to graduates, and are disaggregated by student groups such as race/ethnicity and gender. Under Oregon's Consolidated State Application Accountability Workbook, high school graduation rate targets were set for each year of accountability. Due to the additional time needed to calculate accurate Cohort Graduation Rates, the 2015-16 rates will be used as part of the 2016-17 Accountability Year determinations. This manual provides information on: (1) Changes for the 2015-16 calculation; (2) Cohort calculation; (3) Assigning a cohort year; (4) Identifying students in the state cohort; (5) Determining the final outcome; (6) Determining the Accountable district and school; (7) Determining student group membership; and (8) Appealing cohort graduation rates. Definitions, data sources, resources, and suggested validation checklist are also included. [This document was produced by the Oregon Department of Education Office of Assessment and Accountability.]