OBJECTIVES: The aim of this study was to assess the risk factors of aphthous ulceration (AU) among dental students. METHODOLOGY: This cross-sectional study was conducted at Khyber College of Dentistry, Peshawar in March 2021 among dental students of all four professional years. It was a questionnaire-based study. Questionnaire comprised of demographics and questions about aphthous positivity, risk factors. Risk factors were stress, family history, menstruation (hormonal changes), food allergy, gastrointestinal diseases and medication. Most questions were closed ended. Hospital Anxiety, and Depression Scale (HADS) was used to assess anxiety and depression. RESULTS: Total of 245 dental students responded to questionnaire. Out of 245 dental students, 117 (47.8%) gave a positive history of AU. Mean age in AU positive subjects was 23±1.5 years. AU was seen in males (48.7%) and females (51.3%) with no association between them. Among risk factors, 69 (28.2%) had positive family history, 93 (38%) had stress and 8 (3.3%) reported menstruation. Present study included spice (3.7%), fast food (0.4%), sweets (0.4%), dry fruit (0.4%) and walnut (0.4%) as food allergies related to AU. Only 13 (5.3%) reported a gastrointestinal disease. Medication like NSAIDS and antihypertensive were not involved in any AU case. Anxiety and depression was present in 65% and 38.5% with AU positivity. CONCLUSION: Stress was the most common risk factor and positive family history turned out to be the second common risk factor for AU among dental students.