The survey findings show that parties are a big part of teen life, and alcohol and drugs are frequently present at these parties. Based on the findings, this report advises that parents must assume responsibility for supervising teen parties that are held in their homes. Parents of teens who attend a party at another teen's home should confirm that the parents of that teen will be present in the house during the party and that they will not tolerate the presence of alcohol or drugs. One-third of the teen party-goers had been to parties where teens were drinking alcohol, smoking marijuana, or using cocaine, ecstasy, or prescription drugs while a parent was present. By age 17, nearly half of the teens had been at such parties with parents present. Teens who reported that parents were not present at the parties they attended were 16 times more likely to say alcohol was available, 15 times more likely to report that illegal drugs were available, and 29 times more likely to indicate marijuana was available, compared to teens who reported that parents were always present at the parties they attended. Eighty percent of parents believed that neither marijuana nor alcohol was usually available at parties their teens attended. Survey findings provide a special alert for parents of young teens. The transition from age 13 to 14, often when the move from middle to high school occurs, is a period of sharp increase in the risk for substance abuse. Extensive tables and figures and appended sample performance, survey methodology, screening questions, and questionnaires