The biodegradability and dyeing properties of a series of dextrin-derivative surfactants in direct-dye cotton-dyeing systems have been studied. It was found that these surfactants have good biodegradability, which is lacking in traditional dyeing auxiliaries. In dye-surfactant systems, the degree of aggregation of direct dyes with surfactants was found to influence the rate of cotton dyeing. (c) 2007 Wiley Periodicals, Inc.