The purpose of this article is to present the CT findings in 55 cases of tarsal navicular stress fracture before and after treatment and to describe the CT protocol used.Fifty-five navicular stress fractures in 54 patients whose initial and follow-up CT scans were available for study were retrospectively reviewed. In most cases, contiguous 1.5-mm axial and 3-mm coronal scans of the navicular bone had been obtained. Both feet were scanned for comparison. Follow-up scans were obtained between 4 weeks and 6 years.On review, fractures were evident in all cases, but six small fractures (11%) were missed at the initial interpretation. All fractures involved the central third of the proximal dorsal margin of the navicular bone. Fifty-three fractures (96%) were partial. Forty-three partial fractures were linear, five were linear with bone fragments, and five were rim defects with ossicles. In 13 cases (24%) the fracture was small, 10% or less of bone height. The earliest sign of healing, slight dorsal cortical br...