This paper is a tutorial on the laboratory measurement of sampled infrared imager performance. A review of the classical infrared imager performance measurements that describe sensitivity, resolution, and human interpretation performance is presented. These parameters are Noise Equivalent Temperature Difference (NETD), Modulation Transfer Function (MTF), and Minimum Resolvable Temperature Difference (MRTD or just MRT), respectively. The sensitivity parameters are extended to undersampled imaging systems with 3-D Noise, Inhomogeneity Equivalent Temperature Difference (IETD), and correctability. Also, the measurement of the detector MTF of sampled systems is described using either a scanning slit or tilted edge. Finally, the MRT of sampled systems is a strong function of target to sensor phase. A solution to the phase dependence and sampling limitations is the dynamic MRT, or DMRT. All of these tests are presented in detail and the problems associated with the laboratory measurement of sampled imaging systems are described.