Perchlorate (ClO4-) has emerged as a widespread environmental contaminant and has been detected in various food products and even in human breast milk and urine. This research developed a sensing technique based on surface-enhanced Raman scattering (SERS) for rapid screening and monitoring of this contaminant in groundwater and surface water. The technique was found to be capable of detecting ClO4- at concentrations as low as 10(-9) M (or approximately 0.1 microg/L) by using 2-dimethylaminoethanethiol (DMAE) modified gold nanoparticles as a SERS substrate. Quantitative analysis of ClO4- was validated with good reproducibility by using both simulated and contaminated groundwater samples. When coupled with a portable Raman spectrometer, this technique has the potential to be used as an in situ, rapid screening tool for perchlorate in the environment.