High-intensity focused ultrasound (HIFU) attacks cancer cells by using heat to cause thermal damage, coagulative necrosis, and cell death, leading to creation of a fibrous scar. In a clinical study, dogs received one to 3 treatments for solid tumors that were nonresectable and/or refractory to conventional chemotherapy. Tumor size decreased in 4 of 10 dogs; 2 of 10 dogs exhibited partial remission. All 4 dogs with bleeding from hemorrhagic tumors had alleviated clinical signs. Side effects (ie, hyperthermia, erythema, enteritis, skin ulceration) were mild and self-limiting. This study suggests that veterinary HIFU is a viable alternative treatment for dogs with solid tumors.