OBJECTIVE: Some rheumatic diseases are being influenced by weather conditions. We examined the relationship between oral ulcers and weather/season in Behcet's disease (BD) patients and evaluated the oral ulcers' characteristics by the patients' perspectives. MATERIAL AND METHODS: Patients with BD were evaluated using a self-questionnaire, including patients' clinical and demographical characteristics and detailed characteristics of oral ulcers and the association with season. RESULTS: The most common site of oral ulcers was the tongue (89%). Of 90 patients, there were predisposing factors in oral ulcers. Among patients with BD, 30 believed that seasonal variation aggravated their oral ulcers, especially in winter and autumn. CONCLUSION: The exacerbation of oral ulcers in patients with BD may be related to the seasons. The weather changes in our study are based on the patients' impression; these should be confirmed by objective findings and clinical assessment in further studies.