Precise temperature-composition (T-x) data and excess molar enthalpies (H-m(E)) of binary mixtures of N-methyl-2-pyrrolidone (NMP) with chloroethanes and ethenes were measured by using an ebulliometer and a solution calorimeter. The chloroethanes are 1,2-dichloroethane, 1,1,1-trichloroethane, and 1,1,2,2-tetrachloroethane. The chloroethenes are trichloroethene and tetrachloroethene. The T-x data were used to compute vapor-phase composition and activity coefficients with the Wilson model. The experimental (H-m(E)) values are negative for four binary systems over the entire range of composition. An inversion in sign from negative to positive for the system N-methyl-2-pyrrolidone + tetrachloroethene was observed.