Properties such as semicondutor film grain size, morphology, and channel length are known to effect the sensing response in pentacene based organic thin film transistors (OTFTs). The sensing behavior for low and high mobility pentacene devices are reported here exhibiting different temperature dependent behaviors. The lower mobility OTFT exhibits an expected thermally activated response during alcohol testing with an increasing mobility with temperature along with a decreasing mobility at each temperature for increasing concentration. The higher mobility device exhibits a decrease in mobility with increasing temperature along with a decrease in mobility with increasing concentration at each temperature. In both sets of devices, the polar analyte produced reductions in drain current and shifts in threshold voltage.