Objective: The aim of this clinical study was to evaluate and compare the desensitizing effects of a gallium?aluminum?arsenide (GaAlAs) laser and sodium fluoride (NaF) varnish on dentine hypersensitivity (DH) in periodontal maintenance patients. Background data: The use of lasers opens a new dimension in the treatment of DH. Methods: Forty-eight patients with 244 teeth affected by DH were included in the trial. To be included in the study, the subjects had to have 4 or more hypersensitive teeth at different quadrants. Selected teeth were randomly assigned to a GaAlAs laser group, placebo laser group, NaF varnish group, or a placebo NaF varnish group. Laser therapy was performed at 8.5?J/cm(2) energy density. In the placebo laser group, the same laser without laser emission was used. In the NaF varnish group, the varnish was painted at the cervical region of the teeth. In the placebo NaF varnish group, the same treatment procedures were performed with a saline solution. DH was assessed with a visual analog scale (VAS); immediately, at 1 week, and at 1, 3, and 6 months after treatments. Intra-group time-dependent data were analyzed by Friedman's test, and Wilcoxon's rank sum test was used to evaluate the differences within groups. Results: GaAlAs laser and NaF varnish treatments resulted in a significant reduction in the VAS scores immediately after treatments that were maintained throughout the study when compared to the baseline and placebo treatments. In the NaF group, there was a significant increase in the VAS scores at 3 and 6 months compared to at 1 week and 1 month. The placebo treatments showed no significant changes in VAS scores throughout the study period. Conclusions: Within the limits of the study, GaAlAs laser irradiation was effective in the treatment of DH, and it is a more comfortable and faster procedure than traditional DH treatment.