Intra-oral cancer accounts for approximately 8% of all human malignant diseases. It has been reported that nearly 200 patients per million population in the United States develop carcinoma of the floor of the mouth and tongue each year. Functional study after hemiglossectomy in 26 cases of lingual cancer were studied and the following facts were obtained. 1) Among the six operative group of glossectomy, hemiglossectomy with half resection of mouth floor group occupied high number, 2) Articulation test revealed lower score in hemiglossectomy with half resection of mouth floor group than the hemiglossectomy only group. 3) Tongue movement test showed poor result in hemiglossectomy with half resection of mouth floor cases. 4) Oral diadochokinetic ability declined in the hemiglossectomy with half resection of mouth floor group. 5) Speech function test showed distrotional figure on the consonant T.R.S. except consonant K.