In order to evaluate the Dynasplint Trismus System (DTS) for the relief of trismus secondary to the treatment of head and neck cancer, we conducted a retrospective chart review of patients who had undergone DTS therapy during a 1-year period. Our inclusion criteria were cancer of the upper aerodigestive tract; treatment with radiation, chemotherapy, and/or surgery; and a maximal incisal opening (MIO) of less than 30 mm. MIO and the rate of improvement of trismus ("gain") were measured at selected intervals. Twenty-six patients met our study criteria; their pretherapy mean MIO was 19.3 mm. At the time of their most recent measurement, the mean MIO had increased to 25.5 mm-a measured gain of 32%. Although the initial rate of gain was 0.36 mm/day during the first 6 weeks, improvement leveled off over time, and the overall rate of gain was 0.16 mm/day. We conclude that the DTS is effective in increasing the mandibular range of motion at a rate of change that is maximized during initial treatment.