The objective of this research is to develop a transducer for recognition of molecular changes in the presence of chemical vapors. This transducer is tested using polymer sensing layers known to be sensitive to ethanol vapors. A surface acoustic wave device is selected as the transducer element due to low cost, high surface sensitivity, and sensitivity. These devices are designed and fabricated in-house, and a polymer sensing layer applied. The frequency response of the coated device is probed both with and without the presence of airborne ethanol molecules in a vapor stream. By analyzing the changes in the amplitude and phase of the frequency response near resonance, vapor detection was conclusively demonstrated. Additionally, the mechanism of change was identified, allowing future work in optimizing the sensitivity of the device. Other future work will include application of a biomolecular sensing layer, design of circuitry for a portable devices, and fabrication of a MEMS preconcentrator. The final goal of the project is a portable sensor array using surface acoustic wave devices coated with different bio-molecules.