Studies were carried out in the laboratory to observe the preservative requirements of a variety of industrial and home products, and to determine the efficacy of methylchloroisothiazolone/methylisothiazolone as a preservative for these products. The substrates tested included metalworking fluids, polymer emulsions, distillate fuels, cosmetics, and various household products such as fabric softeners, detergents, floor polishes, floor sealers, etc. Comparisons were made between the efficacy of the isothiazolone compound and that of several of the preservative agents most commonly employed in these products. The results of the studies showed methylchloroisothiazolone/methylisothiazolone to be an effective preservative at very low concentrations for a wide variety of industrial and home products, comparing favorably to preservatives currently recommended for such products.