The U.S. courts consistently have upheld the constitutionality of laws regarding mandatory drug testing policies in the workplace and schools; these policies were designed to detect individuals' drug use that could compromise public safety. Yet looking at the uses of drug test results in another setting—the justice system—reveals one aspect that goes largely unaddressed in these laws and prior research on drug testing: the organizational context surrounding the administration of drug tests that shapes how their results are understood. In response, this article uses ethnographic methods to analyze the ways that staff at a juvenile drug court in southern California interprets drug test results. The article demonstrates that the staff's understandings of drug testing results involve interactional and institutional processes, dependent upon meanings constructed and situated in local organizational contexts.