Statement of problem: "Power Bleaching" which is a new an in-office whitening technique with a combination of a whitening agent (peroxide) and an auxiliary (plasma-Arch light), has been claimed to be an effective and fast method in tooth bleaching. What is more important in using this method is the maintenance of the pulp health after tooth whitening. Purpose: The aim of this study was to evaluate the human pulpal response after bleaching with H2o2  38% and plasma-Arc light.Materials and method: Eighty seven sound first premolars from 27 patients were selected and divided into 3 groups of 29, based on the time intervals of histologic evaluation. In each group 9 teeth were considered as a control. Vitality tests were done before bleaching (base line) and in four intervals of 2, 7, 30 and 60 days, but histologic evaluation was performed in three intervals 2, 7 and 60 days. Immediately after extraction, apical one third of the roots were sectioned off and each specimen was placed in 10% buffered formalin solution for pulpal fixation. EDTA was used for decalcification and sections were prepared from each specimen and stained with H&E and subsequently assessed microscopically for the following criteria: Irregularities in the odontoblastic layer, the presence of inflammatory cell, vasodilatation and pulpal fibrosis. Data was analyzed using Friedman test and Wilcoxon test (α= 0.05).Results: There were significant differences between the 2 and 60 days groups and between 7 and 60 days groups with respect to inflammatory responses and vasodilatation (p<0.05). Comparison of the control and experimental groups of the 2 and 7 days revealed statistically significant differences in inflammation and vasodilatation (p<0.05). No patient had experienced sensitivity, after different bleaching periods.Conclusion: Bleaching of teeth with H2o2 38% and plasma-Arc light might cause slight to moderate pulp reactions after 2 and 7 days confined to the coronal pulp. However, the observed histological changes did not affect the overall health of the pulp tissue permanently.Key words: Power Bleaching- Pulpal response- Human teeth