According to 2002 data from the Maryland Adolescent Survey (MAS), approximately 43 percent of Maryland 12th graders have ever used marijuana while 20 percent used marijuana before age 15. This study used data from the MAS to examine the relationship between the age of marijuana onset and other drug use or problems. The findings indicated that the earlier a student began to use cigarettes, alcohol, and/or marijuana, the more likely it was that they used other drugs. Next, researchers focused on the 20 percent of 12th graders who used marijuana before age 15 and examined all the MAS survey items to identify those related to being an early marijuana user. The result is a scale of nine warning signs for identifying early marijuana users. Recommendations include the implementation of policies and protocols to ensure that students with warnings signs receive appropriate interventions. Tables, figures, footnotes