Isobaric vapor-liquid equilibrium (VLE) data have been measured with a modified Rose-Williams still for the binary systems of methanol (1) + diethylamine (2), methanol (1) + N,N-diethylethanolamine (2), and N,N-diethylethanolamine (1) + diethylamine (2) at p = (60.0 and 101.3) kPa. All of the experimental data pass the thermodynamic consistency test by the method of Herington and the point test of Van Ness. The system of methanol + diethylamine (DEA) at two pressures exhibits a maximum temperature azeotrope. The other two systems did not show that behavior. The experimental VLE data were well-correlated with the Wilson and universal quasichemical (UNIQUAC) activity coefficient models, and the average absolute deviations (AAD) of the vapor-phase mole fraction Delta y between the experimental and the calculated values for all of the measured systems are less than 0.01.