Abstract: This study was designed to evaluate iron deficiency as a predisposing factor for resistant oral aphthosis in patients with Behcet’s disease (BD). Methods: In a case control study 220 consecutive BD patients with oral aphthosis were enrolled. All patients had been treated for at least 3 months. They were divided into two groups according to their treatment response (75 patients in the Case and 145 in the Control group). Demographic and clinical characteristics of the disease, serum iron, total iron binding capacity and serum ferritin were determined in each patient. We used independent t-test and Mann–Whitney U-test to compare the quantitative variables and chi-square test for qualitative variables. Odds ratio (OR) and confidence interval at 95% (95% CI) were calculated for each item. Results: There was no significant difference between the two groups in demographics or clinical characteristics of the disease. We found iron deficiency in 72 patients (32.7%, 95% CI: 6.2), higher in the Case group than Control (39.2% vs. 30.1%; P = 0.17). Despite the higher frequency of iron deficiency in men (26.8% vs. 14.5%), the difference was not statistically significant (P = 0.09). Multivariate logistic regression analysis showed that none of the iron deficiency or sex variables could predict the development of resistant oral aphthosis. The OR for iron deficiency was 1.52 (95% CI: 0.81–2.86) and for male sex was 1.04 (95% CI: 0.56–1.91). Conclusion: Despite the higher frequency of iron deficiency in BD patients with resistant oral aphthosis, we were not able to attribute this resistance to this deficiency. Key words: Behcet’s disease, iron deficiency, oral aphthosis, resistant cases, treatment.