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The efficacy of naphthalene, sulfur, and a commercial combination of these chemicals as a repellent against the plains garter snake (Thamnophis radix) was investigated. Behavioral tests were conducted using 96 recently captured snakes to determine whether significant avoidance results from the presence of these chemicals. Field tests were performed at 24 locations in the snakes' home range and in unfamiliar habitats. In both home ranges and unfamiliar habitats application of potential repellents did not result in significant avoidance behavior. The snakes may be able to sense these volatile chemicals, but the stimuli were unable to alter their behavior. Based on this study, tendency to seek cover, refuge, familiar habitat, or to investigate unfamiliar areas was stronger than deterrence of the chemicals. Because the substances tested did not elicit avoidance behavior in the plains garter snake, usage of these repellents should be discouraged. Habitat modification for snake management is discussed as an alternative to the application of chemical repellents.