Experimental data on the unimolecular degradation of structurally different alcohols, alkanols into water and an olefin and alkenols into a carbonyl compound and an olefin, were analyzed in terms of the method of crossing parabolas. The kinetic parameters characterizing such decomposition were calculated and factors that affect the activation energy of the reaction (the cycle strain energy, the steric factor, and the effect of pi electrons neighboring the reaction center) were determined. The activation energies and the rate constants were calculated for 30 alcohol degradation reactions. The enthalpies, the activation energies, and the rate constants of degradation of unsaturated alcohols were compared for two different degradation routes yielding a carbonyl compound and an olefin or resulting in water and an olefin. Quantum-chemical calculations of the transition states for three model reactions were performed. The activation energies and the rate constants were obtained for the first time for 13 reverse reactions of the addition of carbonyl compounds to olefins.