A gas chromatographic method was developed for the analysis of samples of n-butyl 2,4-dichlorophenoxyacetate, n-butyl 2,4,5-tri- chlorophenoxyacetate, and mixtures of these two compounds. These mixtures are called herbicide orange. Samples of n-butyl 2,4-dichlorophenoxyacetate (four), n-butyl 2,4,5-trichlorophenoxyacetate (four), and herbicide orange (15) were analyzed by gas chromatography. No less than 23 impurity peaks were obtained in the collective chromatograms. Six peaks were the most common impurities. They appeared in a number of chromatograms and often accounted for a major portion of the impurity content. The number and amount of impurities varied considerably in the different samples, even in samples from the same source. The n-butyl 2,4- dichlorophenoxyacetate and the n-butyl 2,4,5-trichlorophenoxyacetate content of the herbicide orange samples was determined by both infrared and gas chromatographic methods. The results from the two methods are compared, and some of the factors which influenced these results and their reliability are discussed.