The analytical properties for a new street drug, 4-methylthioamphetamine (4-MTA), are presented. This new compound was found in tablets sold on the illicit market in the Netherlands and Switzerland in 1997 and 1998. The intermediate 1-(4-methylthiophenyl)-2-nitropropene was also found in a clandestine laboratory in the Netherlands in January 1997. In this study, reference standards were prepared and characterized. The ultraviolet, infrared and nuclear magnetic resonance spectral properties as well as the chromatographic and mass spectrometric (MS) data are reported.