Marijuana is the most widely used illicit drug in Amer­ ica. Some 40% of the adult population has tried mari­ juana at least once. It is the third largest agricultural commodity in the nation and a $10 billion industry. In many areas of the country, marijuana production or sale is the largest moneymaker by far. In Florida, for ex­ ample, it ranks ahead of every business except tourism. It is also a widely misunderstood substance. An en­ tire generation of Americans grew up believing that marijuana was virtually risk-free. This belief persists, despite growing evidence of physical, psychological, and social harm that is caused by the drug. The worst victims of this misinformation are young people. They, of all groups, are the least equipped to uncover and objectively evaluate the evidence regarding marijuana. At the same time, they are the most at risk for long-term problems resulting from marijuana use. v PREFACE vi As physicians we must make every effort to guide young people away from this drug. There are very significant dangers in young people experimenting with marijuana. The drug detoxification center at our hospital-and centers throughout the country-are packed with middle-class young people who started out smoking pot. None of them intended to become addicted, but the fact is that young people are more vulnerable to the influence of the drugs and become dependent easily. They may escalate usage, and progress to use of other drugs.