Statement of Problem: The success rate of light composite restorative treatments is in close relation to the light intensity of the light curing units.Purpose: The purpose of this study was to evaluate the rate of light intensity of visible light curing units, before and after voltage stabilizer application.Materials and Method: This study was performed on 82 light curing units in all clinics and dental offices of Yazd city. For evaluating light exit intensity, Hilux radiometer was used. At first, the light intensity was measured, and then by use of 220 V electrical voltage stabilizer the light exit intensity was recorded. Results were analyzed using Pearson and Spearman tests.Results: Mean range of light intensity before and after voltage stabilizer was 241.3 and 272.6 mW/cm2 respectively. There were statistically significant differences between before and after use of voltage stabilizer (p<0.05). Considering the light intensity, 64.7% of the light curing units were suitable for optimum curing and 8.6% were in group that required increase light exposure time. 21.9% did not completely cure the composites, and 4.8 % were in group with higher light intensity (over 500 mW/Cm2).Conclusion: Light intensity output of the curing units in dental clinics of Yazd city were less than expected, but by using voltage stabilizer, the light intensity was significantly increased.Key words: Light intensity, Light curing device, light meter, Light cure composite, Voltage stabilizer