Field data are presented comparing the efficacy of various disinfectants for the inactivation of ring rot contamination on wooden and on metallic surfaces. Slats of potato crates were inoculated with ring-rot ooze and disinfested in various chemicals. Cut surfaces of healthy seed were then rubbed over the slats to pick up any remaining viable ring-rot bacteria. The seed was planted in randomized replicated rows, and evidence of ring rot survival derived from wilted vines or affected tubers. Disinfectants for wooden surfaces tested in this manner were 1) copper sulfate, 2) mercuric chloride, 3) coal tar phenols, 4) alkyl dimethyl benzyl ammonium chlorides, 5) ammoniacal solution of copper-zinc-phenol, 6) copper naphthanate, 7) chlorinated phenols, 8) N(higher acyl esters of colamino formyl-methyl) pyridinium chloride, 9) calcium hypochlorite, and 10) di-isobutyl phenoxy ethoxy ethyl dimethyl benzyl ammonium chloride. Of these at the concentrations tested, only the first five gave complete control. Disinfectants for metalic surfaces were tested, using screws to simulate such appurtenances of potato production as planters, diggers, and graders. Inoculated and treated screws were thrust into the vascular region of healthy seed, and the seed planted and observed as in the preceding paragraph. Disinfectants for metallic surfaces tested in this manner were: 1) copper sulfate, 2) formalin, 3) alkyl dimethyl benzyl ammonium chlorides, 4) N(higher acyl esters of colamino formyl methyl) pyridinium chloride, 5) di-isobutyl cresoxy ethoxy ethyl dimethyl benzyl ammonium chloride, 6) lauryl isoquinolinium bromide, 7) phenyl mercuri trienthanol ammonium lactate, 8) alkyl dimethyl 3, 4-dichloro-benzyl ammonium chloride pentachlorphenol, 9) sodium paratoluene sulfonchloramide, 10) calcium hypochlorite, and 11) pentachlorphenol. Of these at the concentrations tested, only the first six afforded complete control. Although other chemicals gave control equal to copper sulfate, the latter is the most logical disinfectant to recommend by virtue of its cheapness, its general availability, and its applicability to both wooden and metallic surfaces. Effective concentration for wooden surfaces was found to be 1 pound copper sulfate in 10 gallons water, and for metallic surfaces, 2 pounds in 10 gallons. Data on the 1-pound-per-gallon rate for metallic surfaces are missing.