Photodynamic therapy (PDT) which is a type of photochemotherapy is a new method of treatment used in cases of erosive/atrophic oral lichen planus (OLP) to reduce symptoms of the disease. Assessment of the effect of PDT on pain scale in patients having erosive / atrophic oral lichen planus.30 patients having erosive/atrophic OLP were recruited in this study. The oral lesions were subjected to PDT twice per week for 2 months. Methylene blue (MB) oral gel was used as a photosensitizer applied to the oral lesions, then diode laser of 650 nm WL and 150 mW (milli Watts) powers was used in a non- contact mode for 2:30 minutes. Visual analogue scale (VAS); pain scale was used for clinical assessment. The results showed improvement in the severity of pain over the duration of treatment. There was a gradual decrease of the mean VAS score over 8 weeks duration from 8±1 to 4±2. The decrease was statistically significant in the mean VAS score in the first month from 7±2 to reach 5±2 by the end of the second month (p<0.001). The use of photodynamic therapy was found to be effective in management of erosive / atrophic OLP; it showed improvement in the subjective as well as objective signs and symptoms of the disease with no side effects. Manuscript profile