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The enthalpy–entropy compensation (EEC) phenomenon commonly arises in DNA binding processes, including DNA–peptide interactions, where a rather narrowly defined ΔG value is preserved. Indeed, molecules as large as proteins can share the EEC phenomenon with small ligands, like drugs, despite variations in temperature or salt concentration. For a given series of similar reactions, strict compensation between ΔH and TΔS provides a thermodynamic mechanism which maintains a favourable value of negative ΔG that dominates the binding process. The EEC phenomenon can be categorized into four major types, expressed by the gradient determinant ke of ΔH−TΔS energy compensation. For a given series of ligands, it is their chemical structure and DNA sequence-selectivity which seem to determine the type of energy compensation, manifested by ke, sustaining a favourable negative free energy change within a narrow range that assures successful complex formation.