Gastrointestinal (GI) pythiosis is a severe and often fatal disease in dogs that traditionally has been poorly responsive to medical treatment. Although aggressive surgical resection with wide margins is the most consistently effective treatment, lesion location and extent often preclude complete resection. Recently, it has been suggested that the addition of anti-inflammatory doses of corticosteroids may improve outcome in dogs with nonresectable GI pythiosis. This report describes 3 dogs with colonic pythiosis in which complete resolution of clinical signs, regression of colonic masses, and progressive decreases in serological titers were observed after treatment with itraconazole, terbinafine, and corticosteroids. This treatment protocol represents a promising treatment for dogs with GI pythiosis in which surgical intervention is not feasible.