Results relating to the application of conducting polymers as chemiresistors for the sensing of vapors are reported. In particular, we describe the use of a piezoelectric microbalance with gold electrodes on which we have electrochemically deposited a thin layer of poly(pyrrole). Uptake of a selection of common neutral organic vapors, covering a range of physical properties, is then measured at the same time as measurement of the resistance of a similar thickness of poly(pyrrole) deposited on a narrow-gap resistance probe. Mass uptake and resistance change are considered together to avoid masking the real trends caused by differences in polymer-solvent compatibilities