IMPORTANCE: The timing and indications for repair of orbital floor fractures have been controversial. Current practice dictates that fractures involving more than 50% of the orbital floor should be repaired. Early management is initiated in such situations to prevent long-term sequelae of enophthalmos and diplopia. Because fracture size as measured by computed tomography (CT) is one of the criteria to determine the need for surgical repair, there is a need to know the reliability of this parameter. OBJECTIVE: To assess the variability of CT measurements of orbital floor fractures. DESIGN, SETTING, AND PARTICIPANTS: This study took place between January 1, 2005, and June 1, 2007, at an urban academic medical center. Patients with isolated orbital floor fractures were evaluated by 1 oculoplastic surgeon, and their orbital CT images were subsequently read by 3 neuroradiologists blinded to demographic information and the other readers' measurements. Separately, each was asked to determine the maximal anterior to posterior length and transverse width if a floor fracture existed. MAIN OUTCOMES AND MEASURES: Intraclass correlation coefficients were calculated for length and width using a 2-way mixed-effects model to evaluate the agreement between radiologists. RESULTS: Twenty-three patients met criteria for inclusion in this study (isolated orbital fracture thought to be in need of repair, with diplopia within 30° of primary gaze, and/or enophthalmos >2 mm, and/or 50% of the floor area involved in the fracture). The mean (SD) age of the patients was 31.5 (17.6) years (range, 8-73 years). The magnitude of agreement between the readers as measured by the intraclass correlation coefficient was 0.66 (95% CI, 0.46-0.82) for anterior to posterior length and 0.44 (95% CI, 0.22-0.69) for transverse width, indicating only a moderate degree of concordance. CONCLUSIONS AND RELEVANCE: Although the literature has long held that a floor fracture seen radiographically to involve 50% of the orbital floor has a high likelihood of enophthalmia and should be repaired, this study shows how variable CT measurements of orbital floor fractures can be in a clinical setting, even in trained hands. We question the dependence on such a criterion and reemphasize the importance of making surgical decisions based on clinical findings rather than radiological interpretations.