A sL'C month old intact female pug was presented to the Cornell University Hospital for Animals Soft Tissue Service for evaluation of abnormal urogenital anatomy and ambiguous sex. The patient was otherwise healthy. The major physical exam abnormality was a phallic structure protruding from a ventrally located vulva. Ultrasound revealed uterine horns, abdominal gonads and bilobed soft tissue suggestive of penile musculature within the phallus. The urethral orifice was caudal to the phallus, indicative of hypospadias. A uterus and abdominal testes were removed surgically. Phallopexy and prepuce reconstruction were performed to cover the phallus. A definitive diagnosis of Testicular X,"'{ Disorder of Sexual Development (DSD) was made after histopathology of the reproductive tract and karyotyping. The only treatment complication was persistent exposure of phallic mucosa following surgery, though this was well managed with conse1-vative lubrication at home. The patient has an excellent long-term prognosis. Due to the reported heritable nature of canine XX DSD in this breed, breeding of this patient's parents and littermates is not recommended. This paper describes the clinical approach to DSD and discusses the current understanding of XX DSD mechanisms.