Approximately 90% of patients treated by iontophoresis obtained significant relief from sensitivity elicited by a blast of air and the touch of an explorer. Of those patients that required a second treatment, significant additional improvement was noted in these lesions. Those patients with severe sensitivity initially were the patients who required a second treatment; and those patients with initial mild to moderate sensitivity experienced immediate relief and did not require additional therapy. Hypersensitive lesions are usually located at the buccal cervical margins of teeth, are easily accessible, and are effectively treated by the modern technique of iontophoresis. Iontophoresis appears to be a safe and highly effective means of desensitization of exposed dentinal lesions.