A series of bimetallic catalysts has been prepared by impregnating a commercial Pt/alumina catalyst (series B catalyst in Part I, R. Burch, J. Catal. 71, 348 (1981)) with solutions containing compounds of tin or lead in aqueous or nonaqueous solvents. The activity and selectivity of the catalysts have been determined under flow conditions at 750 K and 1 bar for the conversion of n-hexane, methylcyclopentane, cyclohexane, and at 373 K for the hydrogenation of hex-1-ene. Under these experimental conditions it has been established that the conversion of n-hexane into branched aliphatic isomers is catalysed by a bifunctional mechanism, but excess acidity gives lower selectivity due to enhanced cracking. Benzene and methylcyclopentane are formed directly from n-hexane on metal sites and do not require acidic sites. The conversion of methylcyclopentane into benzene is bifunctional. The results show that when tin is present the catalysts are much more stable, and have much higher selectivities for isomerisation and aromatisation reactions. The Pt-Sn catalysts produce more benzene from methylcyclopentane, they dehydrogenate faster, and they hydrogenate more slowly. At a given conversion the bimetallic catalysts produce much lower concentrations of cracked products. It is concluded that tin modifies the acidity of the support, resulting in higher selectivity for isomerisation and lower selectivity for cracking, and also modifies the properties of the Pt, resulting in less self-poisoning. Taking account of the fact that the tin is mainly present in these catalysts as Sn(II) (see Part I), stabilised by the alumina, it is concluded that the catalytic results cannot be rationalised on the basis of current geometrical models for bimetallic catalysts. It is proposed that the role of the tin is to modify the electronic properties of the small Pt particles. It is tentatively suggested that similar electronic effects may be important in other bimetallic catalysts.