The National Household Survey on Drug Abuse asked respondents to report on their marijuana use, as well as symptoms of dependence on illicit drugs, including marijuana/hashish, cocaine/crack, inhalants, hallucinogens, heroin, or any prescription-type drugs used non-medically. Current marijuana use is defined as use within the past 30 days. Dependence is defined as having symptoms such as increased tolerance, feelings of withdrawal without the drug, and interference with everyday life in the past year. Results show that over one million youths 12- to 17-years-old and half a million young adults 18- to 25-years-old used marijuana for the first time in 1999. In 2000, the highest rate of past month marijuana use was among 19 year olds. Adult dependence on illicit drugs was more likely among individuals that first used marijuana at 14 years or younger than among those that first used marijuana after age 14. The numbers of new marijuana users among youth 12- to 17-years-old increased markedly during the 1990's. An estimated 1 in 20 people used marijuana in the past month in 2000. Use increased for each age beginning at age 12 and peaking at age 19. There were no gender differences in dependence among youth adults reporting first use of marijuana at age 14 or younger. Black and Hispanic young adults that started using marijuana at age 14 or younger were significantly more likely than whites to be dependent on illicit drugs. Young adults with less than a high school education that initiated marijuana use before 14 years of age were more likely to be dependent on illicit drugs than those with more education. 1 table, 4 figures, 2 endnotes