Three 250-m(2)/g SiO2-supported catalysts were prepared, viz., (a) 5%Pd. (b) 5%Pd-5%Bi. and (c) 3%Bi, and used in liquid-phase oxidations of aq. 1 M glucose with oxygen gas (1 L/min) at 1 atm, 333 K and pH 9, to gluconic acid, to study the effect of Bi on the catalytic properties of the system. Each catalyst was predried 2 h/373 K precalcined 4 h/773 K reduced with H-2 2 h/533 K cooled to room temp., flushed with He, and oxidized with (95:5 v/v) He-O-2. Over 2 h long glucose oxidations, catalyst b was superior to catalyst a, but still inferior to Degussa's 4% Pd-1% Pt-5% Bi supported on active C, presumably on account of the SiO2 as carrier in the b and not the Pt in Degussa's catalyst. The b was twice (80-87% in 1-2 h) as selective as the a toward Na gluconate. T-programmed oxidations of individual catalysts a-c showed Pd to become oxidized slowly at room temp., significantly at above 423 K and max. at 580 K, i.e., much above the commercial temperatures of glucose oxidation (<373 M. In catalyst c, the rate of oxidation of Bi was max. at 430 K). The max. oxidation rates of Bi and Pd in the catalysts were consistent in temp. with those of the monometal systems, slight differences being attributable to BiPd andlor Bi2Pd interstitials as evidenced by X-rays. In glucose oxidations run over catalyst b at <373 K Bi is the first metal to be oxidized, which makes deactivation of Pd with oxygen immaterial.