This National Center for Education Statistics (NCES) First Look report introduces new data for two separate measures of 4-year on-time graduation rates as well as event dropout rates for school year (SY) 2010-11 and SY 2011-12. Specifically this report provides the following: (1) Four-year adjusted cohort graduation rate (ACGR) data reported by state or jurisdiction and, for the first time, a national estimated 4-year cohort graduation rate; (2) Averaged freshman graduation rate (AFGR) data by state or jurisdiction and a national estimated AFGR; and (3) High school event dropout rate data by state or jurisdiction and a national estimated event dropout rate. Both the AFGR and ACGR are 4-year on-time graduation rates that provide measures of the percent of students that successfully complete high school in 4 years with a regular high school diploma. Event dropout rates provide a measure of the percentage of students who drop out in a single year. The tables in this report present descriptive information for the United States and for individual states and jurisdictions. The findings chosen for this report provide only a few examples of how the graduation and dropout data may be used. Compared to other measures of graduation rates, the ACGR is considered the most accurate measure available for reporting on-time graduation rates (Seastrom et al. 2006b). A 4-year ACGR is defined as the number of students who graduate in 4 years with a regular high school diploma divided by the number of students who form the adjusted cohort for that graduating class. The term "adjusted cohort" means the students who enter grade 9 plus any students who transfer into the cohort in grades 9-12 minus any students who are removed from the cohort because they transferred out, moved out of the country, or were deceased (34 C.F.R. § 200.19). This First Look provides users with an opportunity to access SY 2010-11 provisional data that have been fully reviewed and edited, and SY 2011-12 preliminary data that have been subjected to a limited data review and editing. Neither set of data have been available publicly prior to the release of this report. Two appendices present: (1) Collection Methodology and Sources of Error; and (2) Detailed Methodology for Calculation of Four-Year On-Time Graduation Rates and Event Dropout Rates. A list of references and related data files is included.