en Multiple Oral Squamous Cell Carcinoma in a Patient with a History of Chemical Warfare Aims: Oral squamous cell carcinoma typically occurs as a primary and solitary lesion, while multifocal cases are considered a rare complication. Various factors have been reported in the literature as contributors to the multiplicity of oral squamous cell carcinoma lesions. Additionally, it is possible that chemical warfare agents, due to their cumulative effects, may play a role in the development of multiple lesions. This study aimed to report an unusual case of multiple oral squamous cell carcinoma in a patient with a history of chemical warfare. Patients & Methods: A 60-year-old male patient with a history of chemical warfare and the chief complaint of a 60-year-old male patient with a history of chemical warfare and a chief complaint of a painful ulcer in his mouth for the past two months was referred to us at Shahid Beheshti Medical University. Findings: An intra-oral examination revealed multifocal white, non-removable, non-homogeneous plaque lesions on the left pterygomandibular area, the left maxillary mucosa, and the anterior mandibular ridge. Incisional biopsies were performed on all lesions. The final diagnosis was early invasive squamous cell carcinoma. Unfortunately, the patient passed away within a few days of the excisional biopsy. Conclusion: In patients with head and neck cancer, particularly squamous cell carcinoma, it may be beneficial to inquire about a history of participation in war in addition to conducting risk assessments. Oral Squamous Cell Carcinoma,Head and Neck Cancer,Chemical Warfare,Sulfur Mustard, 205 209 http://ijwph.ir/browse.php?a_code=A-10-2311-1&slc_lang=en&sid=3 H. Mortazavi 1003194753284600379739 1003194753284600379739 No Department of Oral Medicine, School of Dentistry, Shahid Beheshti University of Medical Sciences, Tehran, Iran H.M.M. Sadeghi 1003194753284600379740 1003194753284600379740 No Department of Oral Medicine, School of Dentistry, Shahid Beheshti University of Medical Sciences, Tehran, Iran S. Dalirani 1003194753284600379738 1003194753284600379738 No Department of Oral Medicine, School of Dentistry, Shahid Beheshti University of Medical Sciences, Tehran, Iran M. Ladanmoghaddam 1003194753284600379737 1003194753284600379737 Yes Department of Oral Medicine, School of Dentistry, Shahid Beheshti University of Medical Sciences, Tehran, Iran