Experimental isothermal P-x data at 313.15 K for the ternary system (tert-amylmethyl ether (TAME) + n-heptane + methanol) and for one of the unmeasured constituent binary systems, (tert-amylmethyl ether (TAME) + methanol) are reported. Data reduction by Barker's method provides correlations for g(E) using the Margules equation for the binary systems and the Wohl expansion for the ternary system. Wilson, NRTL and UNIQUAC models have been applied successfully to both the binary and the ternary systems, The presence of azeotropes in the ternary system and constituent binaries are studied as well as the presence of immiscible zones.