Staff of the Center for Substance Abuse Research developed the SANTA (Substance Abuse Need for Treatment Among Arrestees) methodology. SANTA used trained researchers to interview random samples of adult male arrestees in each of the nine booking facilities in Baltimore, as well as female arrestees in the Central District booking facility, where all arrested women are processed. Each arrestee was asked to participate in an anonymous and confidential interview that used the AutoSANTA instrument, a computerized interview that includes a module of questions designed to assess each arrestee for dependence on alcohol and five classes of other drugs: cocaine, opiates, marijuana, hallucinogens, and amphetamines. Urine specimens and, where possible, samples of scalp hair were collected at the completion of each interview. Over 90 percent of arrestees who were approached agreed to be interviewed, and over 80 percent of those interviewed provided urine or hair specimens. All data on the 1,190 arrestees (755 males and 435 females) interviewed were weighted by age, ethnicity, charge, and district of arrest to reflect the population of adults arrested in Baltimore during the 12-month period. Sixty-nine percent of male and 75 percent of female arrestees tested positive by urinalysis for at least one drug, most often cocaine (54 percent of males and 65 percent of females). Heroin and other opiates were detected in 40 percent of males and 46 percent of females. Funding is needed for additional research to determine the type, duration, and method of treatment most appropriate for persons with longstanding addictions to specific kinds of drugs.