Enophthalmos is usually a consequence of orbital trauma resulting in a blowout fracture of the orbital floor. We report here the case of a 35-year-old male who had a radical operation of the maxillary sinus and the ethmoidal sinus, and 2 months after the operation, developed spontaneous enophthalmos and ocular pain. The left orbit was enophthalmic by 5mm according to Hertel exophthalmometry. Surgical correction was performed under general anesthesia. The left orbit was explored through a transcutaneous incision of the left lower lid which revealed marked periosteal adhesions and absence of the bony floor of the orbit. A rib cartilage graft was used to reconstruct the floor of the orbit, and the globe was brought forward by means of retrobulbar placement. Enophthalmos and ocular pain disappeared postoperatively.