An ultrasonic absorption cell has been constructed that maintains parallelism sufficient for absorption measurements well above 500 Mc/sec. Constructional details are described and results presented showing absorption in benzene, dioxane, and polysiloxane at 510 Mc/sec. The system as a whole will permit an attenuation of about 35 dB before the signal is lost in the noise. The absorption in benzene divided by the square of the frequency is substantially lower than values obtained at low frequencies, and indicates a relaxation frequency of approximately 600 Mc/sec.