The purpose of this study was to determine the role of the fibular free flap in reconstructing lateral segmental defects of the mandible. Over the past 5 1/2 years, 17 consecutive patients underwent reconstruction of their lateral mandible with the fibular free flap. Patients included 12 men and 5 women, the mean age was 54 years (range, 29-76 years), and the mean length of the mandibular defect was 6.3 cm (range, 2.5-9 cm). The majority of patients with tumors (54%) were treated for recurrence and 92% received radiation to the operative field. The mean operative time to perform the microsurgery and bone plating was 4 hours. Postoperative morbidity occurred in 3 patients (18%) (plate fracture, malocclusion, orocutaneous fistula). Five patients (29%) required leg donor site skin grafting. Donor site morbidity included a minor cellulitis, a transient neuropraxia, and one case of leg swelling. None required additional surgery for donor complications. Thus far, 71% of the patients have received dental rehabilitation and 35% had osseointegrated implants placed in their bone flap. Eighty-two percent of the patients achieved both good or excellent aesthetic and functional results. Sixteen patients (94%) tolerate at least a soft diet and 65% are on a regular diet. Five patients developed tumor recurrence an average of 9 months postoperatively with a mean survival of 21 months. This study demonstrates that the fibular free flap is highly reliable for reconstructing the lateral mandible in a single stage, with low overall morbidity, and provides for excellent dental and speech rehabilitation. For most patients, the fibular free flap should be considered for lateral mandibular reconstruction even in those patients with a limited life expectancy.