The standard molar enthalpies of formation at the temperature 298.15 K of (CH3)(2)NPCl2(1), {(CH3)(2)N}2PCl(1), and {(CH3)(2)N}P-3(1) have been determined by reaction calorimetry as -(286.3+/-2.4) kJ.mol(-1), -(220.1+/-2.3) kJ.mol(-1), and -(112.8+/-2.3) kJ.mol(-1), respectively. Enthalpies of vaporization have been obtained from vapour-pressure measurements and the corresponding values of Delta(f)N(m)(degrees)(g) derived as -(245.5+/-2.5)kJ.mol(-1), -(174.2+/-2.6) kJ.mol(-1), and -(71.3+/-2.4) kJ.mol(-1), respectively. The values of the bond enthalpies D(P-Cl) and D(P-N) in substituted phosphines are discussed.