The NSDUH asks persons ages 12 or older to report on their use of alcohol and illicit drugs, as well as their symptoms of substance abuse or dependence in the past year. NSDUH defines dependence on or abuse of alcohol or illicit drugs according to criteria in the Diagnostic and Statistical Manual of Mental Disorders. It mentions such symptoms as withdrawal, tolerance, use in dangerous situations, trouble with the law, and interference in major obligations. NSDUH defines illicit drugs as marijuana/hashish, cocaine (including crack), inhalants, hallucinogens, heroin, or prescription-type drugs used nonmedically. In 2004, 22.5 million people ages 12 or older (9.4 percent) abused or were dependent on alcohol or illicit drugs during the past year. Those who lived in metropolitan areas were more likely to abuse or be dependent on alcohol or an illicit drug during the past year than those living in nonmetropolitan areas. Males living in metropolitan areas were more likely to abuse or be dependent on alcohol or an illicit drug than males living in nonmetropolitan areas. Rates of past-year substance abuse or dependence changed little between 2002, 2003, and 2004 in either metropolitan or nonmetropolitan areas. 3 figures and 4 notes