To evaluate the efficacy of two commercial desensitizing agents in subjects with moderate to severe dentin hypersensitivity for a period of 6 months and to compare the results with topical application of water as negative control.BisBlock (BIS; oxalate) and Gluma Desensitizer PowerGel (GLU; glutaraldehyde/HEMA) were tested. 50 subjects, average age 32.4 years, with at least one cervical hypersensitive incisor, canine or premolar tooth area and pre-operative pain score > or = 6 on VAS from 0 to 10 in each of three quadrants were included. Prior to application of the desensitizing agents or placebo (PLA; water) the sensitive areas were cleaned with prophy paste. Desensitizers were applied according to manufacturers' instructions, the placebo was left for 60 seconds dwell, rinsed off and dried. Pain scores were determined using both evaporative and tactile stimuli immediately after treatment, after 1 day, 1 week, 1, 3 and 6 months. Statistical analyses of the findings were performed using ANOVA and pot-hoc tests with a significance set at P < or = 0.05.All subjects completed the trial. Both the two desensitizing agents and placebo showed significant reduction in sensitivity at baseline and throughout the 6-month evaluation. The effects of the three treatments were significantly different. Pain reduction with GLU was consistently highest, followed by PLA that was significantly greater than BIS. VAS scores for the evaporative stimulus were moderately, but significantly lower than for tactile stimulation.