OBJECTIVE: To identify inciting causes, alternative targets, and risk factors associated with redirected aggression in cats. DESIGN: Case-control study. ANIMALS: 19 cats with a history of redirected aggression and 64 cats with no such history. PROCEDURES: Medical records were reviewed to identify cats evaluated for problems with redirected aggression (case cats), in which the primary inciting stimulus and alternative target of aggression were clearly identifiable. Data obtained from the records and from follow-up interviews included details about the cats and incidents of redirected aggression. Owners of control cats were interviewed via telephone to obtain similar information on their cats. RESULTS: 22 incidents of redirected aggression were reported for the 19 case cats. In 95% of those incidents, loud noises or interactions with other cats were identified as the inciting stimuli. Case cats most commonly redirected their aggression toward the owner, followed by another cat living in the same household. Compared with control cats, case cats were more likely to have a sound phobia but were less likely to be outdoor cats. In addition, case cats were more likely to be from small households (<or= 2 people) than were control cats. In most situations, case cats had adopted a defensive body posture immediately before the incident of redirected aggression, which suggested that the underlying motivation was fear. CONCLUSIONS AND CLINICAL RELEVANCE: Fear was likely the most common motivation for redirected aggression in the cats of this report. To reduce the risk of redirected aggression, veterinarians should encourage owners to socialize kittens and habituate them to novel objects and sounds.