Ultrasonic speeds in the liquid phase of 1,1,1,2-tetrafluoroethane (CF3CH2F) have been measured from 243.11 K to 333.15 K and from near the saturation line to about 30 MPa. The measurements were made using a sing-around technique employing a fixed path acoustic interferometer operated at a frequency of 2 MHz. The probable uncertainty in the results was no greater than +/-0.2% except in the low-density region at near the saturation line at higher temperatures. The vapor pressures have also been observed to within +/-10 kPa by monitoring the acoustic signal at vapor-liquid equilibrium. When these results were combined, the ultrasonic speeds for the saturated liquid were estimated to within +/-1 m . s(-1).