Molecular mechanics calculations (Macromodel v.5.0 and v.8.1) have been used in order to correlate the minimized energies of the complexes with the binding constant Kb values measured on two hosts and five urea derivatives including methyl biotin. Kb values obtained by means of NMR titrations, in the right concentration range between 20 and 80% of saturation, correlate well with the energies provided by the molecular modeling study of the complexes.