Statement of the Problem: Recurrent aphthous stomatitis (RAS) is one of the most common lesions in the oral cavity. Due to its multifactorial nature, there is no definitive treatment for RAS. Laser therapy is one of the suggested treatments to reduce patient’s discomfort.Purpose: The purpose of the present clinical trial is to assess the effect of low and high level laser therapy on pain control and wound healing of RAS.Materials and Method: Thirty six patients with minor RAS were divided into three groups. Group 1 (n=14) received CO2 laser, group 2 (n=12) were treated with InGaAlP Diode laser and group 3 (n=10) received sham laser as placebo. All patients were evaluated daily up to 15 days after receiving one session of laser therapy. Pain severity before and after treatment, wound healing, patient’s satisfaction, and functional disturbance before and after treatment were recorded for each patient.Results: According to statistical analysis, pain reduction after treatment in group 1 was 7.00±2.41, in group 2 was 2.08±2.31, and in group 3 was 1.40±1.77. In addition, a significant difference was observed in the reduction of functional complications in CO2 laser treated patients compared to the other two groups.Conclusion: High-level laser treatment showed analgesic effects on RAS, but no healing was observed. Low-level laser therapy demonstrated no positive effect on recurrent aphthous ulcers. Keywords ● Aphthous  ● Stomatitis  ● Laser therapy  ● Wound healing;