Optimization of an infrared missile seeker requires designing the detector, optics, scanner, control system, and signal processing hardware to 'best' meet the mission performance and physical packaging requirements. 'Best' is usually defined in terms of maximum signal-to-noise ratio and/or minimum acquisition time for various target ranges, target signatures, and atmospheric conditions. This paper presents simulation and experimental results from optimization studies of a gimbal-scanned infrared seeker. The optimization criterion is maximization of the SNR for small targets in the presence of large background variations. The experimental hardware consists of a multi-element detector array, an inertially stabilized gimbal scanned by the gimbal control system, a sensor digital signal processor, and a system computer. The system permits varying the detector angular subtense, scan rate, scan angle, sensor gain, sensor dynamic range, and the acquisition algorithms. The hardware, which includes an imaging radiometer for collecting target signature data, is integrated in a pod flown on a P-3 aircraft. Theoretical optimum values for the variable parameters are derived for generic target conditions by laboratory and computer simulations. Experimental performance of the seeker as a function of the variable parameters is measured and compared to the simulation values. 'Real world' optimization criteria and problems limiting the seeker performance are discussed.