The purpose of this clinical trial was to study the effectiveness of 5% potassium nitrate dentifrice as a daily home treatment of dentinal hypersensitivity. Thirty subjects with dentinal hypersensitivity were included in a 4-week, double-blind, parallel, comparative study. Stimuli used included mechanical, cold water and compressed air blasts. A subjective assessment of the degree of hypersensitivity for each stimulus was recorded. The results indicated that 5% potassium nitrate dentifrice, in comparision with a conventional fluoride dentifrice, reduced dentinal hypersensitivity to a significant degree. The therapeutic response to potassium nitrate was apparent within 2 weeks and increased continuously for the length of the study period. We conclude that 5% potassium nitrate dentifrice is an effective agent for the daily home treatment of dentinal hypersensitivity.