OBJECTIVE To determine the complications observed with using porous spherical orbital implants (hydroxyapatite and porous polyethylene) and the factors leading to their occurrence. METHODS A total of 101 cases of porous spherical orbital implantation by five ophthalmic surgeons were reviewed retrospectively. The demographic data, diagnosis, prior surgery, type and technique of surgery, implant characteristics and prosthesis fitting were described in patients with complications. RESULTS Eleven of the 101 patients had implant exposure. There were six male (1 with bilateral involvement) and four female patients, ranging in age from 2 to 71 years. Preoperative diagnosis included trauma in five patients, nontrauma in five, and tumor in one. Seven had prior eye surgeries. Three patients underwent evisceration, whereas eight underwent enucleation. Eight hydroxyapatite and three porous polyethylene implants were used with diameters of 16 to 20 mm. Three were unwrapped, six were wrapped in sclera, and two were wrapped in preserved fascia. Exposures, which generally occurred within 1 year, were grouped into small (1-5 mm), medium (6-10 mm), and large (> 10 mm). One delayed case occurred after drilling. Small stable exposures were managed conservatively. Larger exposures were managed either by implant revision or replacement. All patients were fit ultimately with a prosthesis. Histopathologic findings of explanted spheres showed fibrovascularization limited to the periphery with moderate inflammatory reaction. CONCLUSIONS Complications were significantly higher in cases of eviscerations than enucleations. Complications occurred in implants either unwrapped or wrapped in homologous grafts. None of the autologous wrapping had exposure. Secondary procedures may initiate exposure when fibrovascular status of implant is inadequate.