The log K, DELTAH, and TDELTAS values for interactions of Na+, K+, Cu2+, and Ca2+ With a series of N,N’-dipivot lariat ethers have been determined from calorimetric titration data valid in 9:1 (v/v) CH3OH/H2O and absolute methanol at 25.0-degrees-C. Complex stability is increased greatly by introducing pendant arms containing oxygen or nitrogen atoms to the parent macrocycles. The enthalpy and entropy changes support the idea that the side arms interact with the cations. Formation of complexes of Ca2+ is both enthalpy and entropy stabilized. All other interactions are enthalpy driven, and the entropy changes are unfavorable. Effects of pendant-arm length and substituents on the complexation of the cations are discussed on the basis of the thermodynamic data. The large negative DELTAH values for complexation of Cu2+ with lariat ethers indicate a strong interaction between Cu2+ and the nitrogen atoms of the ligands. Large entropic losses for some of the cation-ligand interactions indicate that the lariat ethers are flexible and readily change their conformations to accommodate the cations.