In ultrasonic pulse-echo systems, polymers like PMMA (polymethylmethacrylate) and PEEK (polyetheretherketone) are often used as buffer-rods, placed between the ultrasound transducer and the unknown material (liquid, gas, or solid material). Provided the acoustic properties of the buffer-rods are known, it is possible to calculate these also for the unknown material, based on reflections between the buffer-rod and the unknown medium. However, temperature changes also affect these properties. In this paper we present a method for measuring acoustic attenuation, speed of sound and density, for buffer-rod materials. We also give experimental values for PMMA and PEEK, for temperatures between 5/spl deg/C and 37/spl deg/C, and for 5 MHz and 10 MHz ultrasound frequency.