OBJECTIVE To evaluate the efficacy of stereologic methods to measure the orbital volume using computed tomography images of patients with zygomatic fractures. METHODS The present study was retrospectively conducted using hard-copy computed tomography images acquired during the postoperative period of 22 patients with unilateral zygomatic fractures. Orbital volume measurements were performed on the surgically treated and contralateral normal orbits using stereologic methods. The estimates obtained from both sides were compared statistically using the paired samples t test. The measurements were repeated by 2 different observers to estimate the interobserver variability. RESULTS When both observers were taken into account, the mean volume in the normal and surgically treated orbits was 23.6 +/- 3.2 and 24.4 +/- 3.1 cm(3), respectively. A statistically significant difference was noted between the surgically treated and normal orbits (P < .05). The volumes of 16 treated orbits were enlarged by 5.8% +/- 3.8% and 6 were diminished by 2.7% +/- 1.4%. A very high statistical correlation was noted between the 2 observers (R > .95). The total time consumed for calculation in each patient (2 orbits) was 9 to 12 minutes. CONCLUSIONS Stereologic estimation of the orbital volume is an easy, practical, and time-saving procedure that can be performed on readily available, hard-copy computed tomography images. The high interobserver agreement observed in our study shows that it can be safely used in the quantitative detection of preoperative and postoperative volume changes.