Fractures of the frontal sinus with associated serious complications are common and are managed surgically. Twenty-one cases of fracture of the frontal sinus are reviewed. Four of these, initially free of complications and not treated surgically, demonstrated sinusitis six months to seven years post trauma. Obstruction of the nasofrontal duct was a common factor. Impairment of the nasofrontal duct was found in 20 of our 21 cases. Because obstruction of the nasofrontal duct is so common and can lead to sinusitis as a late complication, we recommend surgical exploration of all frontal sinus fractures.