High-pressure vapor-liquid equilibria for the binary carbon dioxide-2-methyl-1-butanol and carbon dioxide-2-methyl-2-butanol systems were measured at 313.2 K. The phase equilibrium apparatus used in this work is of the circulation type in which the coexisting phases are recirculated, on-line sampled, and analyzed. The critical pressure and corresponding mole fraction of carbon dioxide for the binary carbon dioxide-2-methyl-1-butanol system at 313.2 K were found to be 8.36 MPa and 0.980, respectively. The critical point of the binary carbon dioxide-2-methyl-2-butanol was also found 8.15 MPa and 0.970 mole fraction of carbon dioxide. In addition, the phase equilibria of the ternary carbon dioxide-2-methyl-1-butanol-water and carbon dioxide-2-methyl-2-butanol-water systems were measured at 313.2 K and several pressures. These ternary systems showed the liquid-liquid-vapor phase behavior over the range of pressure up to their critical point. The binary equilibrium data were all reasonably well correlated with the Redlich-Kwong (RK), Soave-Redlich-Kwong (SRK), Peng-Robinson (PR), and Patel-Teja (PT) equations of state with eight different mixing rules the van der Waals, Panagiotopoulos-Reid (P&R), and six Huron-Vidal type mixing rules with UNIQUAC parameters.