1. The experience at the I. González Martínez Oncologic Hospital with 157 cases of carcinoma of the floor of the mouth between the years 1940 and 1965, inclusive, is reviewed.2. The sex incidence and etiologic factors are discussed. Carcinoma of the floor of the mouth has been the second most frequent form of cancer of the oral cavity seen in our institution.3. The methods of treatment are discussed and the results of treatment are given in terms of 5 year survival, being 28.1 per cent for the entire series.4. Patients with localized small lesions limited to the floor of the mouth without lymph node metastases (Stage 1 lesions) had the best 5 year survival rate (68.5 per cent).5. The treatment modality which yielded the best results was external irradiation followed by interstitial curietherapy (45.2 per cent), including lesions of all stages.6. The most frequent complication to treatment encountered was radionecrosis of the mandible and/or soft tissues (15 per cent).7. Six patients were treated with irid...