Background:Canine behaviour problems seen by speciality behaviouralmedicine services often involve chronic anxiety disorders that have resultedin maladaptation of the individual to its environment. Common stressorsinclude the presence of other individuals (other dogs or people), noise andbeing alone. The treatment of these behavioural problems usually includesa combination of behaviour modification, environmental modification andbiological therapies. Within the latter, anxiolytic drugs such as clomipramineor fluoxetine have proven useful.Methods:Here, we present a retrospectively analysed series of 32 cases thatwere treated with the anxiolytic drug mirtazapine, which is widely used inhuman medicine but has not previously been reported for the treatment ofbehavioural problems in dogs (although it is marketed as an appetite stimu-lant in cats). Cases included dogs with a range of anxiety-related behaviouralproblems.Results:Eighty-one percent of dogs that presented with a behavioural prob-lem showed improvement and suspected adverse effects were mild andtolerable.Limitations:Further studies are required to isolate this result from the othertherapeutic measures and to compare its efficacy with other drugs.Conclusion:Mirtazapine appears to be a suitable and safe option for thetreatment of anxiety-related behavioural problems in dogs.