In the presence of acid or base, or under neutral conditions, isobutylene is the only observed product of the reactions of tert-butyl alcohol in compressed liquid water at 225, 250, and 320 degrees C. On the basis of a kinetic analysis of limited results at 250 degrees C, an earlier paper concluded that tert-butyl alcohol dissociates as an Arrhenius acid at 250 degrees C and thereby catalyzes its own dehydration to isobutylene. Kinetic analyses of the data sets contained in this paper do not corroborate the alleged ability of tert-butyl alcohol to protonate water. Instead, we find that hydronium ions formed by the ordinary dissociation of water are the primary catalytic agents for the dehydration reaction. In agreement with the earlier work, all three data sets are consistent with a heterolytic reaction mechanism involving protonated alcohol, carbocation, di-tert-butyl ether, and protonated ether as intermediates. The kinetics still suggest that tert-butyl alcohol weakly dissociates as a Bronsted acid at these conditions. Values of K-w determined by the kinetic model enjoy good agreement with electrochemical values available in the literature. Values of the other parameters (rate constants) which compose the kinetic model are evaluated with less precision, and a novel method is proposed to estimate the uncertainty associated with each parameter.