This report presents estimates of the numbers and percentages of adults aged 18 or older with past 12-month mental disorders, as assessed by the Mental Health Surveillance Study (MHSS) clinical study, a subset to the 2008 to 2012 National Survey of Drug Use and Health (NSDUH). The assessment included a modified version of the Structured Clinical Interview for DSM-IV-TR Axis I Disorders (SCID-I). The assessed disorders included mood disorders; anxiety disorders, including obsessive compulsive disorder [OCD], and posttraumatic stress disorder [PTSD]; substance use disorders; eating disorders; other disorders; and a screener for psychotic symptoms. Results are presented by gender, age group, race/ethnicity, family income, education, county type, poverty level, employment, marital status, Census region, and health insurance coverage.