We have used embedded piezoresistive microcantilever (EPM) sensors in the detection of hydrogen cyanide gas. EPM sensors are small, MEMS-based devices consisting of a tiny piezoresistive microcantilever partially embedded into a "sensing material" designed to respond volumetrically when exposed to the desired analyte. These EPM sensors may be very small, operate on simple and inexpensive support electronics, are highly resistant to movement or shock, may be operated by hardwire connection or wirelessly in large numbers, and are capable of detecting many different analytes. In this study, we have used EPM sensors to detect hydrogen cyanide gas. Preliminary results indicate that the EPM sensors provide a fast response (less than 5 seconds) to levels of HCN that may be lethal to humans.