Squamous cell carcinoma of the lower gingiva is a rare lesion that frequently invades the mandible. To determine the factors that affect local disease control and overall survival, a retrospective review of 155 previously untreated patients was performed. Primary lesions larger than 3 cm (P = .021) and persistently disease-positive surgical margins (P = .027) were found to be associated with decreased local control rates. Survival was adversely affected by advanced T stage (P = .001), positive initial and final surgical margins (P = .004), mandibular invasion (P = .014), and cervical metastases (P<.001). Extent of mandibular resection, tumor extension beyond the lower gingiva, recent dental extractions in the region of the primary, perineural invasion, and histologic grade did not affect local control or survival. Although lower gingival carcinoma tends to involve the mandible, our findings indicate that tumor size is more important than mandibular invasion in predicting local disease control. Larger tumors that have a greater propensity for local recurrence and poorer survival require a more extensive surgical resection.