The measurement of moisture in paper with reflected infrared radiation is unique in many of its properties, not the least of which is the ability to detect moisture at the very surface of the paper. This study quantifies the surface moisture measurement via a computer simulation of the infrared sensor and paper medium. Three basic areas are considered: 1) the theory behind a sensor and radiation model; 2) a description of a computer simulation based on these models, plus subsequent experiments performed to test these simulations; and 3) a comparison of theoretical and experimental results. Virtually all of the measurement information gathered by a reflection-style infrared sensor is returned from the first 10 g/m₂ of the paper surface. -- AATA