Abstract: Behcet's disease (BD) is not rare in children, and it's clinical picture differs from that in adults. We studied 66 patients in whom the disease was diagnosed under the age 16 from a population of 2068 BD patients. Comparison of the results with the adults by the student paired t test showed: although the most frequent initial manifestation of BD in children was oral aphthosis (54.5%), it was less frequent than in adults (73%. P < 0.0008). Uveitis as the initial manifestation was more frequent (30% vs 12%, P = 0.00002). Mucosal and skin manifestations of the disease were seen less in childhood (oral aphthosis: 77% vs 96%, genital aphthosis: 26% vs 65%, both with P< 0.000001, skin lesions: 61% vs 78%, P<0.0006). Ophthalmological lesions were more prevalent as anterior uveitis (67% vs 51 %, P< 0.02) and posterior uveitis (68% vs 50%, P< 0.004). Joint involvement in children presented itself mostly as arthralgia. Arthritis was less encountered (14% vs 33%, P < 0.0005). We did not see any form of vascular involvement in children. HLA typing showed a higher frequency of HLA-B27 (21% vs 10%, P < 0.002). The complete form of the disease (Japanese Criteria) was less in children (6% vs 32%, P < 0.000001). To find if these differences will remain after the age of 16, we studied a group of 296 patients in whom the first manifestation of the disease had begun before the age 16. It was notable that genital ulcerations (55% vs 65%, P < 0.002), phlebitis (6% vs 10%, P < 0.02) and complete form of the disease (25% vs 32%, P < 0.04) would be less encountered in these group, even in the long term follow-up (mean 11.9 years). Another important point is that the International Criteria is not suitable for diagnosing BD in children because of mandatory oral aphthosis. This cause a delay in diagnosis (only about half of the children have oral aphthosis as the initial manifestation), while having a low sensitivity (23% of the children never developed oral aphthosis before 16).