This article presents a case of bilateral ethmoid sinusitis with unilateral proptosis as a presenting sign of an unsuspected prostate carcinoma. A 59-year-old Hispanic male presented to his primary care physician with nasal congestion and rhinitis. He was treated with antibiotics and antihistamine decongestants for 3 weeks without improvement. A trial of steroids resulted in brief improvement followed by a rapid onset of nasal obstruction with proptosis. A computed tomography scan revealed opacification of the ethmoid sinus with right proptosis. The presumptive diagnosis was orbital cellulitis secondary to chronic ethmoid sinusitis. Endoscopic sinusotomy and bilateral ethmoidectomies were performed. Biopsy results returned as metastatic adenocarcinoma, probably of prostate origin. Urological work-up and evaluation with biopsy confirmed the diagnosis of prostatic carcinoma. The patient was treated with chemotherapy and radiation therapy. He died 7 months later with disseminated disease.