The effectiveness of potassium nitrate (5%, delivered in a low abrasive toothpaste vehicle) as a daily home treatment of dentinal hypersensitivity was evaluated in a 4-week, double-blind, parallel, comparative study of 27 subjects with the condition. Hypersensitivity levels in affected teeth were assessed by two quantifying methods--electrical stimulus and cold air stimulus--and by a subjective recall procedure. The results from these three methods of assessment indicate that potassium nitrate desensitizes hypersensitive teeth to a significant degree. The therapeutic response (decline in dentinal hypersensitivity) to potassium nitrate was evident within 1 week and increased continuously for the length of the study period. Sensitivity threshold of teeth adjudged to be normally sensitive were not altered by treatment with potassium nitrate, nor did the agent exert any discernable effects on oral tissues.