Experimental PVT data have been obtained for isopropyl alcohol by the use of a constant-volume apparatus. Smoothed values of the compressibility factor are presented for temperatures from 200° to 300°C. and pressures from 1,000 to 8,000 lb./sq. in. The experimental data are estimated to be accurate to within 0.4%. The compressibility factor of isopropyl alcohol is also analyzed by the fourth-parameter approach. It is shown that the normal fluid relationship for the compressibility factor can be extended to polar fluids by the inclusion of linear and quadratic terms in the fourth parameter.