As a component of Maryland’s Drug Early Warning System (DEWS), the Juvenile Offender Population Urinalysis Screening (OPUS) study implemented in 1998 by the Center for Substance Abuse Research (CESAR) is a urinalysis-monitoring program for juveniles processed by the Department of Juvenile Services (DJS) to monitor changes in drug use and identify emerging drugs of abuse among the juvenile offender population. The Juvenile OPUS Project is in two parts: intake and detention. Under the intake study, interviews and urine specimens are obtained once a year from youths being assessed in DJS county offices. Under the detention study, only urine specimens are obtained from youth newly admitted to the DJS’s five detention facilities. This report presents major findings from the OPUS Intake Study from September 2002 to May 2003 for nine counties and Baltimore City. Highlights include: (1) juveniles throughout Maryland reported that marijuana was the most popular and most accessible drug in their communities; (2) marijuana’s popularity was confirmed by urinalyses; (3) ecstasy remains a popular drug of abuse among juveniles in Maryland; and (4) many youth reported that dipping tobacco or marijuana cigarettes in PCP is more popular than in the past. The report also presents major findings from the OPUS Detention Study from January 1999 to June 2003 for five participating detention facilities which include: (1) youths, during this time period, were most likely to test positive for marijuana; (2) urinalysis test results showed little ecstasy use; and (3) overall, the percentage of youths who tested positive for marijuana increased with age; by age 16, almost one-half of youths tested for marijuana. Tables