The paper is concerned with the geometric calibration of infrared imaging systems with a view to use them in both photogrammetry and remote sensing applications. From the geometric point of view, three quite different types of infrared imagers can be distinguished: 1. the pyroelectric vidicon camera; 2. the CCD camera with 2-D areal array of solid-state detectors; and 3. the thermal video frame scanner (TVFS). These operate in different parts of the infrared spectrum. The special optical and detector technologies used in these different devices are first reviewed. On this basis, a special target plate is constructed with its own internal radiation source that allows all of these devices to be calibrated geometrically. The actual experimental and calibration procedures are described, as is the method used for the automated measurement of all the targets using image matching techniques. The subsequent data processing and analysis are then outlined. The results obtained from the successful calibration of a representative sample of CCD cameras and thermal video frame scanners are presented and discussed in detail. They provide much new and accurate information on the geometric characteristics of these imagers that can be used in military, medical, industrial, and environmental applications.