We reviewed our experience with 320 patients treated for squamous cell carcinoma of the floor of the mouth from 1964 through 1977. The patients were evenly distributed according to clinical stage. Treatment consisted of surgery (77 percent of patients), surgery and adjunctive radiation therapy (19 percent of patients), or radiation therapy only (4 percent of patients). Most of the patients with favorable (T1) primary tumors had a simple peroral excision (78 percent) with marginal mandibulectomy when indicated (22 percent). Marginal mandibulectomy was still possible in many patients with T2 or T3 lesions (56 percent). Synchronous or metachronous second primary cancers were documented in 33 percent of the patients, most of which occurred in the head and neck region. Seventeen percent of the patients who had elective neck dissection had microscopic metastasis. More than a third of the patients with clinically positive nodes had negative neck specimens histologically. In patients with histologically positive nodes, 60 percent had involvement at multiple levels. The 5 year determinate cure for the entire group was 65 percent. According to stage, 88, 80, 66 and 32 percent of patients with stages I, II, III, and IV disease, respectively, were alive and well 5 years after treatment. This seems to be a significant improvement when compared with the last report from our hospital.