One hundred eighty-three patients with floor of the mouth cancer, of whom 162 were evaluable, were treated between 1962 and 1987. Most patients (139) received treatment with curative intent. Forty-seven received surgery only; 45 received radiotherapy (RT) only; 23 received preoperative RT and surgery; 24 received surgery and postoperative RT. A subset of 30 patients received brachytherapy and external beam RT. Overall survival rates were: surgery only, 90%/68% (2 years/5 years); RT only, 65%/45%; preoperative RT, 65%/43%; and postoperative RT, 78%/41%. Patients receiving surgery generally had lower stage disease and good performance status; RT patients generally had higher stage disease--(64% had stages III and IV disease). Patients receiving RT also had over twice the incidence of deaths from intercurrent disease. These were the contributing factors to the lower survival rate of the patients receiving RT. Disease-free survivals were similar between the groups. In contrast, locoregional control was better for patients receiving RT, particularly in the postoperative RT and brachytherapy groups. Locoregional control rates were: surgery only, 59%/52% (2 years/5 years); RT only, 78%/69%; preoperative RT, 75%/58%; postoperative RT, 80%/74%; and brachytherapy, 96%/89%. This advantage in locoregional control was marked in patients with advanced local disease and was evident at 2 years and beyond. Treatment approaches evolved during the study period toward the use of surgery only in lower stages and combined with RT (usually postoperative) in higher stages.