Authorities across the globe are struggling to keep up with the synthesis of illicit designer drugs—psychoactive compounds modified to avoid existing drug laws. One way Austria is monitoring new substances on the street is through the Federal Ministry of Health-funded CheckIt! project. A mobile team of scientists and counselors periodically travels to large music events and tests drugs submitted anonymously by attendees using liquid chromatography/mass spectrometry. Within 30 minutes, the group posts the results, letting the user know whether the drug they thought they paid for was what they actually got. But LC/MS doesn’t tell the team anything about the psychoactive action of drugs or drug mixtures, says Rainer Schmid, scientific director of the project. So Schmid and Harald H. Sitte, both at the Medical University of Vienna, and coworkers developed an approach that combines LC/MS with a cell assay to get more information (ACS Chem. Neurosci., DOI: 10.1021/cn3001763). The assay tests whether a street drug either blocks or reverses the flux of monoamine transporters—membrane proteins that shuttle neurotransmitters in and out of nerve cells. Comparing these results with those of known drugs, such as the amphetamine Ecstasy, the researchers accurately predict what types of compounds exist in some otherwise difficult-to-assess street drugs.