The ultrasonic absorption and reflection properties of sexually mature, freshly excised mouse, rabbit, cat, and dog testes were investigated at 37.degree. C in the frequency range 0.5-7 MHz by the transient thermoelectric absorption, the pulse-reflection and the pulse-transmission methods. The absorption coefficient exhibited values considerably less than those of other parenchymal tissues and had a frequency dependence mimicking a simple relaxation process of characteristic frequency approximately 0.9 MHz.