The kinetics of the tetralin hydrogenation in decane was studied on a Ni/gamma -Al2O3 catalyst over a temperature range of 85-160 degreesC and a pressure range of 20-40 bar. The hydrogenation occurred by sequential steps from tetralin to cis- and trans-decalins with the formation of octalins as reaction intermediates. Besides the hydrogenation some dehydrogenation to naphthalene was observed in addition to severe catalyst deactivation. The hydrogenation followed low-order rate towards tetralin and close to first-order towards hydrogen. The proposed kinetic model based on a Langmuir-Hinshelwood-type mechanism included the tetralin hydrogenation through intermediate steps to cis- and trans-decalin. The model was able to describe the experimental results adequately and gave physically meaningful parameters.