The tests were conducted between June and November 1987 in New York City; Washington, D.C.; New Orleans; San Diego; Indianapolis; Phoenix, Ariz; Los Angeles; Houston; Chicago; Detroit; Fort Lauderdale, Fla.; and Portland, Oreg. The National Institute of Justice (NIJ) sponsored the testing with cofunding by the Bureau of Justice Assistance. NIJ will sample new arrestees four times each year, and 25 cities are expected to participate. In this sample, 53 to 79 percent of the arrestees tested positive for illicit drugs. The sample was tested for 10 drugs: cocaine, heroin, marijuana, methadone, methaqualone, phencyclidine (PCP), Valium, Darvon, amphetamines ('speed'), and barbiturates. Wide differences were found in the number of users who tested positive for two or more drugs. For example in New York, Washington, and San Diego, at least 20 percent of those arrested were found to be positive for two or more drugs other than marijuana. Other findings indicate cocaine use has surpassed that of marijuana in New York City and the District of Columbia; heroin remains a significant and continuing problem in New York, Washington, Detroit, San Diego, Chicago, Portland, and Los Angeles; and in New York, one in four arrested persons were found to have heroin in their bodies. The use of barbiturates, methaqualone, Valium, Darvon and illegal methadone in most cities was less than previously surmised. Two graphs.