The combination of incoherent elastic and quasielastic neutron scattering with neutron diffraction has been used to show the formation of a two-dimensional crystalline monolayer of dodecanoic acid in equilibrium with heptane solution. The molecules in the monolayer are found to be lying with their long axes parallel to the surface. This solid monolayer melts at approximately 1.15 times the melting point of the bulk solution.