The relative permittivity of HFC 134a, HFC 32, and HFC 125 was measured as a function of temperature and pressure, to cover the liquid and gaseous states. The temperature range studied was 303 to 403 K, and the pressure range was 4.0 to 30.0 MPa. The relative permittivity, epsilon, could be fitted to the reduced density rho(r) using the function (epsilon - 1)/(2 epsilon + 1). The dipole moment of HFC 134a in the liquid phase has been calculated.