The ultrasonic speeds in the liquid phase of 1,1,1,2,2-pentafluoro-3,3-dichloropropane, CF3CF2CHCl2 and 1,1,2,2,3-pentafluoro-1,3-dichloropropane, CClF2CF2CHClF, which have been developed as new cleaning agents, were measured by a sing-around technique operated at a frequency of 2 MHz. The measurements were carried out at 283-343 K and pressures up to 30 MPa with an uncertainty within +/-0.2%. The results for each isotherm show the linear relation with densities and are correlated by the Tait equation with a reasonable accuracy in the whole range of conditions. It is found that these substances, showing lower ultrasonic speed similar to that in 1,1,2-trichloro-1,1,3-trifluoroethane, CCl2FCClF2 have excellent characteristics of cleaning agents.