Abstract: Introduction: Behcet's disease (BD) is underdiagnosed in children. It is mainly due to the wide range manifestations of the disease, the low specificity of the symptoms, and the unfamiliarity of most physicians with childhood BD. These patients are not included in the juvenile group and may be a cause of controversy in the description of BD in children. The aim of this study was to find if the characteristics of juvenile BD differ when diagnosed before or after the age of 16, and to compare them with adults in whom the disease started in childhood. Materials & Methods: In a cohort of 3729 patients with BD, three groups selected. 1- Patients under the age of 16, as childhood diagnosed (CDBD). 2- Patients in whom BD developed before the age 16 but was diagnosed after 16, as childhood completed (CCBD). 3- Those in whom the onset of BD was before 16 but the disease developed after 16, as adult completed (ACBD). Different manifestations of the disease were compared by the chi square test. A confidence interval at 95% (CI) was calculated for each item. Results: There were 49 patients in CCBD group and 113 patients in CDBD group. The age of onset was slightly higher in the CCBD group (12.6±3.1 vs. 10.7±3.3, p<0.0009). It was associated with a higher frequency of mucous lesions (p<0.02), both oral (p<0.03) and genital aphthosis (p<0.000001); vascular lesions (p<0.02) and G.I. involvement (p<0.0l). The frequency of skin and joint involvement was higher (p=0.09), and ocular lesions was seen lower (p>0.6) but all were not statistically significant. The frequency of other clinical and paraclinical data showed no significant difference between these two groups. As the first manifestation, mucous lesions were more common notably genital aphthosis (31%+13 vs. 6%+4, p=0.00001). There was 363 patients in the ACBD group with a mean age of 12.6±3.4 at onset. Comparison of this group with the CDBD group showed, a higher age of onset (p=0.000002). It was associated with a higher frequency of mucous lesions (p<0.000001), skin (p=0.00008) and vascular involvement (p<0.03), but ocular lesions were seen less (p<0.02). As the presenting sign, the frequency of oral aphthosis was higher (82%±4, p<0.0004) and the uveitis lower (6%+2.4, p<0.000001). Comparison of the CCBD group with the ACBD group showed only higher frequency of the genital aphthosis, both at onset (p<0.000001) and during the course of the disease(p<0.02) in CCBD group. Conclusion: Patients known as juvenile BD (CDBD group in this study), are those with more severe forms of the disease (notably with eye involvement). The delay in diagnosis of milder forms of the disease may be an explanation for some of the differences reported between the adult and the juvenile forms. We suggest to include this form of the disease (CCBD group) as juvenile BD in future studies.