Otitis externa is the most common disease of the ear canal in dogs. This disease is painful, causes extreme discomfort and requires immediate treatment. Negligence in the treatment and management of animals can lead to chronic otitis and/or otitis media, which can result in impairment of the vestibulo-cochlear apparatus and rupture of the tympanic membrane, leading to loss of hearing and quality of life. This book emphasizes the importance of individualized clinical-pathological and laboratory evaluation associated with the etiology in cases of canine otitis externa, with a view to choosing the appropriate therapeutic protocol for successful treatment. In addition to describing the clinical-pathological aspects of otitis externa in naturally affected domestic dogs and evaluating sensitivity in vitro and clinical efficacy in vivo, it aims to provide useful information for the development and application of diagnostic measures, effective treatments, prevention and control, thus guaranteeing hearing health and animal welfare.