This study examined tongue function and its relation to swallowing in 13 subjects with oral or oropharyngeal cancer treated with primary radiotherapy +/- chemotherapy and 13 age- and sex-matched control subjects. Measures of swallowing and tongue function were obtained using videofluoroscopy, pretreatment and 2 months posttreatment. Maximum isometric strength and endurance at 50% of maximum strength were obtained with the Iowa Oral Performance Instrument (IOPI). Control subjects were tested once. All subjects with head and neck cancer were evaluated pretreatment and 2 months posttreatment. No significant differences were found for the tongue function measures pre- and 2 months posttreatment in the group with head and neck cancer. Significantly higher tongue strength was observed in the control than in the group with head and neck cancer both pre- and posttreatment. No significant differences were found for the 2 groups for tongue endurance measures. Significant correlations of tongue strength and endurance and some swallow measures were found pre- and posttreatment for the group with head and neck cancer and for the control group. These correlations included oral and pharyngeal temporal swallow measures and oropharyngeal swallow efficiency. Pretreatment differences between the 2 groups in tongue strength were likely related to tumor bulk, pain, and soreness. Two-month posttreatment differences were likely related to radiation +/- chemotherapy changes to the oral and pharyngeal mucosa. This study provides support for the hypothesis that tongue strength plays a role in oropharyngeal swallowing, particularly related to the oral phase of the swallow.