A series of patients whose urine screened positive for 3,4-methylenedioxymethamphetamine (MDMA) using a commercial enzyme immunoassay test (Ecstasy EMIT II assay), failed to confirm by substance-specific liquid chromatography-tandem mass spectrometry tests for MDMA. Further evaluation of these urine specimens indicates that they were positive for trazodone and its metabolite meta-chlorophenylpiperazine (m-CPP). Independent tests of standards showed significant crossreactivity on the Ecstasy EMIT II assay with trazodone, m-CPP, and the related recreational drug trifluoromethylphenylpiperazine (TFMPP). This is of further forensic significance because m-CPP is emerging as an illicit recreational drug in its own right or as an adulterant in illicit cocaine and MDMA. The hallucinogen benzylpiperazine was also assessed but found not to cross-react significantly with this assay. Patients taking trazodone may get false-positive results on the urine EMIT test for MDMA.