The cloth swatch olfactometric technique uses flannel swatches to absorb odors for presentation to a trained human sensory panel. This study examined the reliability of the refined cloth swatch technique used to facilitate the quantification of odor offensiveness of swine facility wastewater treated in subsurface-flow constructed wetlands. Reliability was based on the consistency of ratings assigned by panelists to odor sample replicate pairs. Panelists assigned odor replicate pairs ratings that differed by +/-0 or +/-1 with a 79% frequency, while differences of +/-0 and +/-1 between odor replicate pairs would occur with only a 44% frequency if ratings were randomly assigned. Although individual panelist error during individual trials varied among panelists, individual panelist error over all trials was found to be not significant (Z < 115, alpha=0.05). Statistical methods described here could be used to screen human sensory panelists during pre-trials. Overall, the swatch olfactometric technique used by human sensory panelists yielded highly consistent results and low overall error, indicating that odor offensiveness rating data obtained using the refined cloth swatch technique were reliable to use for various odor analyses.