In the present photoionization study of tert-butyl alcohol, the parent ion of the deuterated isotopomer [(CD3)(3)-COH] was observed and an ionization energy (IE) of 9.82 +/- 0.02 eV was derived from a step-function threshold at 126.25 nm. The appearance energies (AE’s) of (CD3)(2)COH+ and (CH3)(2)COH+ were also determined (at 298 K) to be 9.84 +/- 0.02 and 9.86 +/- 0.02 eV, respectively. From these results, the IE of undeuterated tert-butyl alcohol (which was not observed) was estimated to be 9.84 +/- 0.03 eV. The difference between the IE and the derived AE(0) (AE = 10.01 +/- 0.03 eV at 0 K) implies an upper limit of 0.17 +/- 0.04 eV for the barrier to dissociation of (CH3)(3)COH+. A recent evaluation of the proton affinity of acetone was employed to derive a value of 5.40 +/- 0.10 eV for Delta(f)H degrees(0)[(CH3)(2)COH+] and, thence, the enthalpy of reaction, Delta(f)H degrees(0) = 9.87 +/- 0.11 eV; and from this, an upper limit of 0.14 +/- 0.11 eV for the reverse barrier of the dissociation was obtained. RRKM calculations were performed by using the energies derived from the experimental (and estimated) values. For excitation energies greater than or equal to 0.2 eV above threshold, RRKM calculations yield large rate coefficients for dissociation. Also, the kinetic energy release (KER) was calculated for various models of the dissociation complex. The calculated KER’s are consistent with experimental values when it is assumed that only 5 of the 38 vibrational modes of the transition state are active in the randomization of internal energy.