Activity results for n-butane and n-pentane isomerization activity on a mesoporous and conventional sulfated zirconia are presented as a function of pretreatment and reaction conditions. During both reactions, rapid deactivation occurs followed by a low residual activity. The activity is shown to be a strong function of the extent of hydration of the catalyst. Regeneration in oxygen must be followed by a step that results in the rehydration of the catalyst to recover the original activity. The optimal activities of both a conventional and a mesoporous sulfated zirconia catalysts also depend on the drying procedure used. A two-site model consisting of Lewis and Bronsted active sites is proposed to explain the two regimes of deactivation observed on these catalysts.