25,26,27,28-Tetrahydroxycalix[4]arene-5,11,17,23-tetrasulphonate was in a heat-conduction calorimeter titrated with alpha,omega-alkyl diammonium ions, +H3N(CH2)(n)NH3+ n=(3-7), in an aqueous solution at pH 7.1. Apparent concentration binding constants (K-c) and enthalpy changes are reported for a 1 : 1 binding model at minimized concentration ranges. The standard Gibbs energy change, Delta G(0)=-RTln K-c, has a non-linear dependence of the alkyl chain length, n. The interaction is strongest at n greater than or equal to 5. A similar trend is observed for the enthalpy change. However, the fit of the experimental data to the 1 : 1 model was quite poor and neither 1 : 2 nor 2 : 1 models gave any further improvement. Concentration-dependent results were also obtained. It is therefore concluded that the interaction observed is more complex.