Thermal decomposition of (CH3)(2)C(OH)CD3 in a static reactor and in a shock tube reactor led to intramolecular symmetry-corrected k(H)/k(D) kinetic isotope effects for eliminations of HOH and HOD of 1.80 +/-0.08 at 436 to 481 degreesC and 1.54 +/- 0.12 at 813 to 883 degreesC. Calculations with B3LYP/6-31G* theory defined the transition structure for the 1,2-elimination reaction, the internal reaction coordinate path, and k(H)/k(D) predictions. The reaction takes place through a four-centered transition structure approached through very different progressions of bond length changes along the reaction coordinate.