Multiple-angle incidence resolution spectrometry (MAIRS) is a potentially useful spectroscopic technique for quantitative analysis of molecular orientation in thin films deposited on a solid substrate. Although the technique is based on a unique measurement concept and theory, it can easily be equipped on a commercial FT-IR and the operation is user friendly. In this review, representative application studies of MAIRS are summarized as well as a recent new theoretical approach to get over a conventional experimental limitation that a high-refractive-index substrate is necessary for quantitatively reliable MAIRS analysis.