The Drug Abuse Warning Network (DAWN) focuses on metropolitan areas to reveal emerging drug problems before they become widespread. DAWN detects new drugs, new drug combinations, new health consequences of drug use, and changing patterns involving old drugs. Communities can use this information to plan, target resources, and act more effectively. Of the nearly 2.4 million visits to Chicago area emergency departments (ED's), about 1 percent (32,454) were related to drug abuse. The most common drugs involved in these visits were cocaine, heroin, alcohol, marijuana, and narcotic analgesics (pain relievers). Cocaine-related ED visits rose 47 percent from 1995 to 2002. Between 1995 and 2002, the rate of heroin-related ED visits increased 167 percent (from 83 to 220 visits per 100,000 population). The 2002 rate of heroin-related ED visits was more than 6 times the national rate of 36 visits per 100,000 population. The rate of marijuana-related ED visits rose 52 percent from 1995 to 2002. Almost three-quarters of marijuana-related ED visits in 2002 involved other drugs. From 1995 to 2002, ED mentions of pain relievers rose 96 percent with an increase of 56 percent from 2000 to 2002. During 2002, methadone, hydrocodone, and codeine were the most frequently named pain relievers in drug abuse-related ED visits. Among the 21 DAWN areas, Chicago ranked in the top 3 in terms of ED visits involving cocaine and heroin.