OBJECTIVE: The aims of this study were to evaluate the therapeutic outcome and morbidity associated with management of squamous cell carcinoma (SCC) T3-T4 of the floor of the mouth. PATIENTS AND METHODS: This was a retrospective study (1993 and 2005). Inclusion criteria were: 1) Presence of a locally advanced (T3-T4) lesion of the floor of the mouth; 2) Pathological confirmation of SCC; 3) No previous treatment of the floor of the mouth; 4) Absence of any synchronous lesions at the primary endoscopic work-up; 5) Absence of distant metastasis outside the aero-digestive tract; 6) Karnofsky performance index > 70. All patients were treated by surgery and adjuvant radiotherapy. The statistical analysis was conducted using the stat-view software; categorical variables were compared using the Fisher's exact test; analysis of recurrence-free survival rate was done following the Kaplan-Meier method, and the log-rank test was used for the comparison of survival graphs. RESULTS: Fourty-seven patients were included in this study (42 men), of a mean age of 53.3 years. The majority of patients (93.6%) presented with a stage IVa tumour and no clinical evidence of cervical lymphadenopathy in 60% of cases. All patients underwent bilateral neck dissection adapted to the cervical lymph node status. Forty-one (87%) patients underwent partial mandibulectomy with fibula free-flap reconstruction in 32 cases (78%). Early local complication rate was of 32%. The mean duration of hospitalization was 34 days. Late local complication rate was of 17%. The immediate post-operative death rate was 2%. The rate of survival and recurrence free survival was of 47.5% and 47% respectively. The 3 survival-influencing factors were age (p = 0.02), margins of surgical resection (p = 0.002), and histologic cervical lymph node status (p = 0.03). CONCLUSION: T3-T4 tumours of the floor of the mouth are managed by surgical resection and adjuvant radiotherapy. There is a high rate of treatment-associated complications. The prognosis of locally advanced tumours of the floor of the mouth remains humble.