While marijuana use among high school seniors increased by 38 percent, the proportion of those who believe marijuana is harmful dropped by 22 percent during the 1992-1995 period. Changes in perceptions and knowledge may be due to a decrease in antidrug messages in the media, an increase in prodrug messages through the pop culture, and lack of awareness among parents about the resurgence of drug use. In addition, because many parents experimented with marijuana when they were in college, they often find it difficult to talk about marijuana use with their children and to set strict rules against drug use. To help parents and children review scientific facts about marijuana and to encourage open communication about drug use, information is provided on types of marijuana and how marijuana is used, ways of determining if children use marijuana, reasons why young people use marijuana, whether marijuana leads to other drug use, effects of marijuana use, pregnancy and marijuana use, drug addiction, the use of marijuana as a medicine, and how to prevent children from getting involved with marijuana. 12 references and 19 photographs