Equilibrium constants for the liquid-phase synthesis of 2-methoxy-2-methylbutane (TAME) and 2-ethoxy-2-methylbutane (TAEE) were measured in the temperature range 323-363 K. The equilibria were studied using the alcohol/alkene mixture in various mole ratios and the respective ether as a reagent in a batch reactor. A commercial cation exchange resin (Amberlyst 16) was used as the catalyst. The system was strongly nonideal, and the UNIQUAC estimation method was used in the calculation of the liquid-phase activity coefficients. The experimental equilibrium constants are given as a function of temperature. At 333 K the equilibrium constants K(a) for the synthesis of TAME were 39.6 +/- 2.5 from methanol and 2-methyl-1-butene (2M1B) and 4.1 +/- 0.3 from 2-methyl-2-butene (2M2B). The equilibrium constants for the synthesis of TAEE were 17.4 +/- 1.1 from ethanol and 2M1B and 1.7 +/- 0.1 from 2M2B. The experimental DELTA(r)H values for the liquid-phase synthesis of TAME were -33.6 +/- 5.1 kJ.mol-1 (2M1B) and -26.8 +/- 2.3 kJ.mol-1 (2M2B), and those for the synthesis of TAEE were -35.2 +/- 5.8 kJ.mol-1 (2M1B) and -27.3 +/- 6.7 kJ.mol-1 (2M2B). The results were compared with the literature values.