Marijuana is the most commonly used illicit drug in this country. Forty-eight percent of teenagers have tried marijuana by the time they graduate from high school. Marijuana is a far more potent drug than it was 30 years ago. It is an addictive drug with serious and perhaps long-lasting side effects. Marijuana use impairs a person’s ability to form memories and recall events, as well as the ability to shift attention from one task to another, making school work and learning difficult. Marijuana affects perception, judgment, coordination, balance, and motor skills, impairing driving ability and the performance of young athletes. Marijuana takes a toll on the body, especially the heart and lungs. Marijuana affects people’s everyday lives and the lives of those around them just as other drugs of addiction do. Long-term marijuana use can lead to addiction in some people. They seek out and take the drug compulsively, regardless of whether it interferes with their family life, school, work, or recreational activities. Long-term users not only crave the drug when they try to stop, but also experience withdrawal symptoms such as irritability, restlessness, difficulty in sleeping, loss of appetite, weight loss, shaky hands, and anxiety. Marijuana can worsen psychotic symptoms in people with schizophrenia, and high doses of THC can induce psychosis. Treatment programs aimed specifically at marijuana abuse are few, partly because many people use marijuana in combination with other drugs like cocaine or alcohol. Smoking marijuana may increase the likelihood of cancer of the respiratory tract and lungs. Marijuana raises blood pressure and heart rate and reduces oxygen-carrying capacity of blood, thus resulting in a dramatically increased risk of cardiac arrest. Long-term studies of the patterns of drug use of high school students show that very few young people use other drugs without trying marijuana, alcohol, or tobacco first. Community anti-drug coalitions need to address the growing problem of marijuana use by getting parents involved, letting teens know the truth about marijuana, educating the community, and supporting treatment.