Abstract: Background: Our purpose was to show different aspects of the muco-cutaneous lesions of Behcet’s disease (BD). Although they are not specific, they constitute the major symptoms in all sets of diagnosis criteria for BD. Methods: Description of muco-cutaneous lesions seen during 12 years follow up in 4605 patients. Results: 1- Mucous-membrane lesions: Recurrent oral aphthosis (OA) is the most important and frequent lesion of BD. It resembles the other OA of other etiologies. It was seen in 96.6% ± 0.5 of patients. The number and the size of OA varied in the same patient in each recurrence. The classification in major and minor OA is of no interest. The giant OA and Miliaria aphthosis were rare. Genital aphthosis (GA) was seen in 65.1% ± 1.4 of cases. Seen more often on the scrotum in male, and on the vulva in females, it is lager than OA and often let cicatrix. Sometimes the aphthous lesions can be localized around the anus. 2- Skin lesions. The frequency of the skin lesions was 70.5% ± 1.3 of patients. Skin hyper sensitivity to traumatism was 58.2 %±1.4. Behçet’s Pustulosis is the most frequent cutaneous lesion of BD, seen in 62.3%±1.4 of cases. Small round erythemato-edematous lesions are a round and painful erythemato –edematous lesions. Cutaneous aphtosis is less frequent but it is the most characteristic lesions of BD. Behçet cellulitis is a large painful erythemato-edematous lesion. Pyodermagangrenosum like lesions is exceptionally seen. Subcutaneous lesions were seen in 22.2%±1.2 of patients. They are painful sub cutaneous nodules with often an erythemato-edematous compound. They can rarely become confluent, and exceptionally suppurative. The pathology of all these lesions is a vasculitis. Conclusion: BD lesions are not specific, but their coexistence and their own characteristics may help the diagnosis, which may be missed in countries where the disease is less frequent.