Reaction kinetics studies were conducted of n-butane and isobutane isomerization over sulfated zirconia at 423 K. The kinetic data can be described well by a rate expression based on a reversible, bimolecular surface reaction between two adsorbed n-C-4 species, probably through a C-8 intermediate, to produce one i-C-4 species, as well as surface reaction between two adsorbed i-C-4 species to produce one n-C-4 species, This reaction sequence also describes well the rates of C-4-disproportionation reactions to produce C-3 and C-5 species. The initial rate of catalyst deactivation is faster during n-butane isomerization than during isobutane isomerization, and the longer-term rate of deactivation during n-butane isomerization increases with the pressure of n-butane. The more rapid catalyst deactivation during n-butane isomerization may be related to the formation of n-C-4-diene species.