The isomerization of 1-butene to cis- and trans-2-butene and isobutene has been studied on boron phosphate (BP) catalysts with PIE ratios from 0.8 to 1.4 and at various reaction temperatures and contact times. Isobutene forms on BP with PIE ratios of 1.2 or higher on which relatively strong Bronsted acid sites exist and increases with reaction temperature up to 400 degrees C. Although deactivation of the catalyst occurs, the activity and selectivity to isobutene can be maintained by the continuous injection of small quantities of water into the feed stream. The conversion and selectivities are related to the formation of carbocations on Bronsted acid sites on the high P/B compositions.