Background/Aims: There is controversy related to the role of smoking in affecting the clinical features of patients with Beh？et’s disease (BD). The aim of this study was to investigate the effect of smoking on clinical manifestations in Korean BD patients. Methods: We enrolled 131 patients with BD who fulfilled the International Study Group (ISG) criteria of 1990. The disease-related clinical features of BD―oral ulcers, genital ulcers, ocular lesions, arthritis, vascular lesions, gastrointestinal lesions―and central nerve lesions, smoking history, disease duration, and the presence of HLA-B51 were retrospectively assessed through medical record reviews and patient interviews. Statistical analysis was performed using Chi-square, Fisher’s exact, or student t-test, if appropriate. Results: The frequencies of vascular and gastrointestinal lesions in smokers were significantly increased compared to those in non-smokers (p=0.040, OR=3.341, 95% CI 1.083-10.305; p=0.012, OR=3.878, 95% CI 1.