Thermally grown native oxides of indium have the reputation of being rather poor‐quality tunneling barriers when indium is used as the base electrode. We have developed a simple technique in which a freshly evaporated indium film is allowed to oxidize in the presence of acetic‐acid vapor prior to the deposition of the lead counterelectrode. These easily reproduced tunnel junctions are of extremely high quality with Josephson critical current densities as high as 5000 A/cm2. Auger, electron energy loss, and ellipsometry studies reveal that there is a thinner and more uniform oxide coverage on the acid‐oxidized films when compared to air‐oxidized films. The absence of a pronounced Auger carbon peak on the tunnel junction samples, together with infrared evidence for acetate ion formation on indium samples exposed to significantly higher partial pressures of acetic‐acid vapor, suggest that there is an absorption/desorption process in which a submonolayer amount of ionized acetic acid serves as a structural relaxation catalyst at oxide sites which are at higher energy than would occur in a uniform lattice.