A retrospective evaluation of 5 cases of orbital or intraocular porcupine quills in the dog and a literature review from MEDLINE (1983-1995) is presented. This paper reviews the diagnosis, therapy, and visual prognosis of ocular and orbital quills in the dog. Distinguishing penetration and perforation of the eye and intraocular structures is paramount in establishing a visual prognosis and appropriate therapy. Perforation of the cornea or sclera, lens, or the uvea and retina necessitates prompt specialized surgical therapy to save vision. The diagnosis of orbital quills can be readily confirmed with ultrasonography. The characteristic sonographic appearance of a double-banded, linear, hyperechoic object allows accurate localization of the quill, which aids surgical removal.