The ability of the Peng-Robinson equation of state (PR EOS) to calculate the high-pressure, multiphase behavior of select binary systems has been examined using K- and L-points (also referred to as critical end points) in phase space as key landmarks and adjusting the attractive term binary interaction parameter (delta(12))The ethane + ethanol system showed a transition from type 11 behavior to type III behavior as delta(12) increased, but the type V phase behavior exhibited experimentally could not be calculated with any value of delta(12). The equation of state incorrectly calculated type V phase behavior for the methane + n-pentane system, which experimentally shows type I behavior. The type V behavior of the methane + n-hexane system was qualitatively calculated with delta(12) = 0.014 giving the best fit to the experimental L-point while the type V behavior of the methane + n-heptane system was calculated, but the three-phase line failed to extend below the experimental four-phase point temperature and pressure (which experimentally masks the L-point). The propane + fluorene and propane + anthracene binaries showed type V behavior with a three-phase line extending below the experimental four-phase point pressure and temperature with delta(12) = -0.05 and delta(12) = 0.01, respectively. Calculations with the propane + triphenylmethane binary showed that a constant binary interaction parameter could not produce a three-phase line extending below the four-phase point, suggesting a limitation of the PR EOS to model this system's multiphase fluid-solid behavior.