The fecal pellets of rabbits,Oryctolagus cuniculus, are coated with secretion from the anal gland, the odor from which functions as a territorial marker. The total volatiles collected from above fecal pellets and three different fractions prepared by washing the volatiles through either distilled water, 1 M sodium hydroxide, or 1 M hydrochloric acid were tested for their effect on the territorial confidence of individual animals. Tests were based on the neutral pen paradigm used in previous studies but employed a specially designed test chamber, the internal odor environment of which could be fully controlled. In the four series of bioassays a total of 140 separate tests were performed and 64 adult male rabbits were used. The results showed that the presence of the total volatiles influences the outcome of territorial competitions in pairs of male rabbits in favor of the individual from which they were derived. They were comparable with those obtained in earlier studies when fecal pellets were presented in the test pen. The effects of the different washing reagents on the total odor are illustrated by gas chromatograms, and the components most likely to be removed by the different treatments are suggested. The volatiles remaining after passing through distilled water had less effect on the rabbit's behavior than the total odor. Since the washing process not only removed water-soluble compounds but also led to a reduction in the concentrations of water-insoluble components introduced into the test chamber, either of these factors could have been responsible for the weakened effect. Fractions of the odor obtained by washing with either sodium hydroxide or hydrochloric acid did not influence the results of the tests. This suggests that the essential components of the olfactory signal include both basic and acidic compounds.