Orbital infections account for the majority of primary intraorbital disease processes. Sinusitis is the most common etiology. Five stages of cellulitis secondary to sinusitis have been described. Systemic conditions which predispose to orbital infection include diabetes, septicemia, malignancy, and immunosuppresion. Clinical signs and symptoms include superficial inflammatory changes, as well as proptosis, limitation of extraocular motility, and visual loss. Causative agents are most commonly bacteria, with fungus, viruses, and parasites seen less frequently. Imaging is performed by CT and/or MRI which are complementary in certain cases. Differential diagnosis of imaging abnormalities includes inflammatory and granulomatous diseases, as well as neoplasm.