In the United States, nearly two-thirds of all deaths among young people aged 10-14 years result from only five causes: motor-vehicle crashes (23.4%), other unintentional injuries (15.7%), cancer (12.5%), suicide (7.2%), and homicide (5.2%). Across all age groups in the United States, the leading causes of illness and death are related to the following behaviors: (1) Risk behaviors that contribute to unintentional injuries and violence; (2) Tobacco use; (3) Alcohol and other drug use; (4) Sexual behaviors that contribute to unintended pregnancy and STDs, including human immunodeficiency virus (HIV) infection; (5) Unhealthy dietary behaviors; and (6) Physical inactivity (and overweight). These behaviors are frequently interrelated and are often established during youth and persist into adulthood. To monitor priority health-risk behaviors among adolescents and young adults in each of these six categories, the Centers for Disease Control and Prevention (CDC) established the Youth Risk Behavior Surveillance System (YRBSS). The YRBSS includes national, state, and local school-based surveys of high school students in grades 9-12. In addition, some states and cities conduct a school-based Youth Risk Behavior Survey (YRBS) among middle school students. In 2005, 10 states and 11 cities conducted a middle school YRBS. This report summarizes results from five state and eight local middle school surveys with weighted data in 2005. With the exception of one local survey (San Francisco) conducted during fall 2004, all weighted surveys were conducted during spring 2005. Data from the five state and two local school-based surveys with unweighted data are not included in this report. 2005 Middle School Youth Risk Behavior Survey Questionnaire is appended. (Contains 261 tables.)