The vapor pressures of (monoethanolamine (MEA) + water) and (4-methylmorpholine + water) and of all the pure components were measured by means of two static devices at temperatures between (283 and 363) K. The data were correlated with the Antoine equation. From these data, excess Gibbs functions were calculated for several constant temperatures and fitted to a fourth-order Redlich-Kister equation using Barker's method. The (4-methylmorpholine + water) binary system shows maximum azeotropic behavior over the whole temperature range. The (MEA + water) binary mixture exhibits negative deviations in G(E); whereas for the (4-methylmorpholine + water) system, the excess Gibbs energy is positive for all investigated temperatures over the whole composition range.