Infrared(IR) fiber optic radiometry of thermal surfaces offers several advantages over refractive optics radiometry. It does not need a direct line of sight to the measured thermal surface and combines high capability of monitoring small areas with high efficiency. These advantages of IR fibers are important in the control of nonuniform temperature and emissivity distributions, in which the parameters of closely situated points differ considerably and a high spatial resolution is necessary. The theoretical and experimental aspects of such radiometry are discussed in this report.Theoretical and experimental radiometric output functions of the sensor during scanning of an area with a nonuniform temperature and emissivity distributions were obtained and their dependence on the spacial location of the fiber and type of distribution were analyzed. The results suggest that IR fiberoptic radiometry will be useful in industrial, medical and domestic applications. 370