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 coefficientswere 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). Themagnitude 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.