The brown dog tick, Rhipicephalus sanguineus sensu lato, which may actually include more than 1 species, is a vector of the hemoparasites Babesia vogeli, Ehrlichia canis, and Hepatozoon canis and can also cause direct damage (eg, anemia, eczema, flaccid paralysis) to hosts. Tick control is primarily achieved with acaricides that act as broad-spectrum neurotoxins; however, overuse of these agents has led to acaricide resistance. Some animals are “tick-resistant” and produce signaling chemicals (semiochemicals) that mediate the behavioral biology of the tick and naturally control parasitism. There are conflicting reports about whether domestic dogs are capable of such tick resistance. Recent evidence suggests that tick resistance depends on breed of dog; ticks feeding on beagles were under-developed compared to those feeding on English cocker spaniels. The purpose of this study was to identify semiochemicals from beagles that may mediate repellency against R sanguineus. The investigators performed chemical analysis on beagle- and cocker spaniel-odor extracts using coupled high-resolution gas chromatography-mass spectrometry and Petri dish and olfactometer behavioral assays to assess the response of ticks to identified compounds. The beagle-odor extracts contained almost 3 times as many chemical compounds as cocker spaniel samples, with 2-hexanone, benzaldehyde, and undecane found to be repellant for R sanguineus. Findings from this study may enable development of new products for control of this particular tick species.