The most recent set of climatic normals, 1971-2000, involved a substantial change in the manner in which temperature data are collected. As many first-order stations converted to an ASOS (Automated Surface Observing System) array of instruments, as a way to more efficiently collect data, the changeover impacted the calculation of the monthly climate temperature normals. In previous in-situ studies, ASOS sensors were shown to measure a slightly cooler temperature than previous instruments. The National Climatic Data Center (NCDC) adjusted the 1971-2000 normals at some stations to compensate for this potential "bias." By comparing First Order stations utilizing ASOS for a relatively substantive portion of the 30-year period against a similar period in the surrounding Cooperative Network station record, an inhomogeneity in the data for the ASOS-commissioned stations will be revealed. This paper will discuss the methodology for undertaking such a statistical study and offer evidence of the impact that ASOS has in the calculation of the 1971-2000 climatic normals.