The reactions of n-hexane, 2,2-dimethylbutane and methylcyclopentane in excess hydrogen were studied on alumina-supported Pd-Re catalysts characterized by medium metal dispersion. Palladium is much less active than rhenium in catalyzing alkane conversions, Even very small amounts of added rhenium to palladium cause big catalytic consequences. All Re-containing samples behave similarly, i.e. exhibit comparable activation energies (much lower than in the case of Pd/Al2O3) and a radical loss of isomerization capability. Accordingly, examination of these variables cannot effectively serve in probing Pd-Re surfaces. However, other useful 'fingerprints' have been recognized, among which the fragmentation factor in alkane conversions and the 2MP/3MP product ratio in methylcyclopentane reaction are the most valuable. Their profound specific variations with Pd-Re composition clearly suggest that rhenium interacts with surface palladium atoms.