Experimental thermodynamic property data for hydrocarbon refrigerant mixtures are more important now in order to improve the performance of existing equations of state. In the present paper, liquidphase PVTx data including bubble points for the binary and ternary systems composed of propane (1), n-butane (2), and isobutane (3) are reported. More than 1000 measurements were made by employing a newly developed vibrating-tube densimeter system with an uncertainty of 0.1 kg(.)m(-3) + 0.024% for density, (3 to 7) mK for temperature, 0.26 kPa + 0.022% for pressure, and 0.1 mol % for composition. The present data contain the first set of experimental PVTx data for the ternary system. The measured data are compared with two available thermodynamic mixture models developed by Lemmon and Jacobsen and Miyamoto and Watanabe. A mixture model applied for a modified Tait equation of state is also presented in this paper.