In order to give a solid foundation of the description of the motion of the three-phase contact line, we develop the nonequilibrium thermodynamic description of the contact line. It is postulated that during its motion the contact line is featured as a separate thermodynamic system. Conservation laws are given for the excess densities of the components, the momentum and the energy along the line. The Gibbs law is formulated for the contact line and using this law the excess entropy production density along the line is constructed. This identifies the conjugate thermodynamic forces and fluxes for the contact line. Linear laws relating these quantities can then be given. The special case considered by Shikmurzaev, who gave the first satisfactory description of the motion of the contact line, is considered in more detail. A new boundary condition is found, which was not used by Shikhmurzaev. The need for such an additional boundary condition for this case was discussed in recent work by Billingham. (C) 2004 American Institute of Physics.