The dehydrogenation of butene-1 over a chromia-alumina catalyst has been used to study the distribution and concentration of the coke deposited along a fixed bed reactor using different feed concentrations of butene-1. Axial temperature measurements showed a steep initial temperature minimum followed by a subsequent shallower minimum. Corresponding coke profiles were determined using a microbalance and confirmed by the non-invasive neutron attenuation technique. These together with determinations of exit gas concentrations suggest that coke is formed primarily from the reaction product butadiene, and that this coke deposit limits further formation of this product and thus decreases further coke formation.