Twenty-two navicular stress fractures sustained during athletic activity were retrospectively reviewed for return to activity time and the appearance of fracture pattern on computerized tomography. There were 10 females and nine males, with the average patient age being 27.2 years. Three patients sustained bilateral injuries at separate times. Average follow-up was 36.5 months. Nine patients underwent open reduction, internal fixation (some with bone grafting); this group's average return to activity (RTA) was 3.1 +/- 1.2 months (range, 1.5-5 months). Thirteen patients treated conservatively had an average return to activity of 4.3 +/- 2.8 months (range, 2-13 months). The difference between the two groups' RTA was significant (p = .02). Eleven patients utilized pulsed electromagnetic fields (PEMF) and had an average RTA of 4.2 +/- 3.4 months, 27.3% of those patients with PEMF also had surgery. Two conservatively treated fractures that took 5 and 8 months to RTA, respectively, re-fractured during the treatment process. Retrospective review showed CT fracture patterns in the frontal plane that were classified as: dorsal cortical break (type I), fracture propagation into the navicular body (type II), and fracture propagation into another cortex (type III). This is a proposed classification system. It includes modifiers "A" (avascular necrosis of a portion of the navicular); "C" (cystic changes of the fracture), and "S" (sclerosis of the margins of the fracture), the latter of which was most common in our series, particularly in continually symptomatic patients. Type I fractures were more likely to receive conservative treatment (p = .02) and type III fractures took significantly longer to heal than types I and II (p values .001 and .01, respectively). Type I and II injuries had an average RTA of 3.0 and 3.6 months, respectively. Type III injuries had an average RTA of 6.8 months. Based on our findings, we recommend surgery for patients with these modifiers, particularly with type II and III injuries. Conservative treatment may be prolonged, and requires at least 6 weeks of nonweightbearing in a below-knee cast/boot to be successful.