Purpose: To report the incidence of orbital cellulitis after orbital blowout fracture. Design: Retrospective, noncomparative, interventional case series. Participants: All patients with orbital cellulitis and a history of recent orbital fracture. Methods: A medical record review of clinical history, imaging studies, and surgical and treatment outcome was performed. Main Outcome Measures: Resolution of orbital cellulitis and surgical and imaging findings. Results: Four patients (3 male; mean age, 30 years range,4.5-58) were treated for orbital cellul itis complicating orbital fracture. All patients had evidence of paranasal sinusitis before or after the orbital injury, and 2 also reported forceful nose blowing after sustaining orbital trauma. Although 3 patients received prophylactic oral antibiotics after the fracture, this failed to prevent infection. Sinusitis commenced 1 to 2 weeks before and as late as 5 weeks after orbital injury. All patients were treated with IV antibiotics. Two developed an orbital abscess that required surgical drainage; 1 patient improved after an endonasal maxillary antrostomy. One patient improved on IV antibiotics alone and underwent fracture repair at a later stage. These 4 patients represent 0.8%of all cases of orbital frac tures treated in the study period. Conclusions: Orbital cellulitis is a rare complication of orbital fracture, and seems to be more common when paranasal sinus infection preexists or occurs within several weeks of the injury. Oral antibiotics given after the orbital injury may not prevent orbital cellulitis or abscess formation. Surgerymay be required to drain orbital abscess or in nonresolving cellulitis to drain the paranasal sinuses. Fracture repair, if indicated, should be delayed, particularly if an alloplastic implant is used. Purpose: To report the incidence of orbital cellulitis after orbital blowout fracture. Design: Retrospective, noncomparative, interventional case series. Participants: All patients with orbital cellulitis and a history of recent orbital fracture. Methods: A medical record review of clinical history, imaging studies, and surgical and treatment outcome was performed. Main Outcome Measures: Resolution of orbital cellulitis and surgical and imaging findings. Results: Four patients (3 male; mean age, 30 years range, 4.5-58) were treated for orbital cellulitis complicating orbital fracture. All patients had evidence of paranasal sinusitis before or after the orbital injury, and 2 also reported forceful nose blowing after sustaining orbital trauma. 3 patients received prophylactic oral antibiotics after the fracture, this failed to prevent infection. Sinusitis commenced 1 to 2 weeks before and as late as 5 weeks after orbital injury. All patients were treated with IV antibiotics. Two developed one orbital abscess that required surgical drainage; 1 patient improved after an endonasal maxillary antrostomy. One patient improved on IV antibiotics alone and underwent fracture repair at a later stage. These 4 patients represent 0.8% of all cases of orbital frac tures treated in the study period. Conclusions: Orbital cellulitis is a rare complication of orbital fracture, and seems to be more common when paranasal sinus infection preexists or occurs within several weeks of the injury. Oral antibiotics given after the orbital injury may not prevent orbital cellulitis or abscess formation . Surgerymay be required to drain orbital abscess or in nonresolving cellulitis to drain the paranasal sinuses. Fracture repair, if indicated, should be delayed, particularly if an alloplastic implant is used.