Stomatitis in dogs is commonly associated with severe periodontal disease, renal failure, trauma, immune-mediated diseases, infection secondary to immunosuppression (diabetes mellitus, hyperadrenocorticism), and ingestion of caustic substances. Similar to cats with lymphocytic-plasmacytic gingivitis stomatitis, dogs present an inflammatory condition in the oral cavity called ulcerative stomatitis, idiopathic stomatitis, or lymphocytic-plasmacytic stomatitis. An 8-year-old male Cocker Spaniel dog was presented for clinical examination with oral pain, dysphagia, severe halitosis, and diffuse hyperemia of the gum. The striking lesion was multiple ulcers on the gingiva of the caudal teeth where the buccal mucosa at the commissures contacted the tooth, and opposite the upper incisive teeth (also known as "kissing ulcers") with adjacent gingival recession and dehiscence, and accumulation of partially chewed food at these sites. The superior incisive teeth were mobile. An initial treatment with chlorhexidine, associated with antibiotic therapy with spiramycin plus metronidazole, and meloxicam for 10 days was recommended. The dog was then reevaluated and showed good recovering. However, 56 days later, the dog was brought again to the clinic and chief complaints were head pain when touched by the owner, and swelling of the upper lip. At that time, the same clinical features observed at the first physical examination were present. Radiographs revealed alveolar bone absorption around superior incisive teeth. Incisional biopsies were taken from the affected gingiva. Histologically, the lesion was characterized by severe interstitial lymphoplasmacytic infiltrate in the superficial corium of the gingiva. The epithelium was multifocally ulcerated and covered with variable layers of fibrin and neutrophils. In the remaining epithelium, areas of hydropic degeneration with mild hyperplasia were seen. Since auto-immune diseases were ruled out based on histopathological changes, a diagnosis of lymphoplasmacytic stomatitis, similar to those seen in cats was established, and the same treatment was performed. After 21 days of treatment with clindamycin and prednisone, there was partial resolution of the clinical signs. Since then, recurrent clinical signs appear when conservative treatment is interrupted. Repeated intermittent treatment has been performed to control the severity of the clinical signs. As in feline stomatitis, the underlying pathogenesis is unclear. It is suggested that this condition is an inflammatory rather than infectious process. If the conservative management with medications and home care are no longer effective, often selective teeth extractions are recommended.