The effect of colchicine was evaluated in a large cohort of Behçet's disease (BD) patients and compared to placebo. In a randomized, double-blind, controlled crossover trial, 169 patients without major organ involvement were selected consecutively. They fulfilled the International Criteria for Behçet's Disease. Patients were randomly assigned to colchicine or placebo. At 4 months, they were swapped over (colchicine to placebo, placebo to colchicine) for another 4 months. The primary outcome was the overall disease activity index, the IBDDAM. The secondary outcome was the responses of the individual symptoms. A Student's paired t test was used to evaluate results within each group, and an ANOVA to check for differences between colchicine and placebo. Analysis was performed using the "intention to treat" method. For placebo, IBDDAM worsened from 3.17 to 3.63 (t = 1.750, P = 0.08). For colchicine, IBDDAM improved from 3.35 to 2.75 (t = 4.143, P < 0.0001). Oral aphthosis, genital aphthosis, pseudofolliculitis, and erythema nodosum improved significantly with colchicine but not with placebo. According to the ANOVA, the difference in IBDDAM between colchicine and placebo was highly significant (F = 14.674, P = 0.00016). The difference between the results for males and females was not significant (F = 0.181, P = 0.67). In conclusion, colchicine, but not placebo, significantly improved the overall disease activity index. The difference between the results for colchicine and placebo was also statistically significant.