Acoustooptic beam deflectors are finding increased application at infrared wavelengths. For deflectors operating at, say, 10.6 μm, the large drive powers required for efficient operation will heat the deflector material and may cause degradations in beam quality. To determine the extent of such thermal degradation in practice, the performance of an 800-spot and a 200-spot germanium deflector have been measured in our laboratory. Test results have shown less than 1/2 λ/D beam-quality degradation over time constants of one minute or less. These laboratory results have confirmed our theoretical expectations, which were based on a time-dependent thermal model of the acoustooptic deflector. Extensions of our analysis to other candidate infrared materials will be discussed.