Abstract: Introduction: The diagnosis of Behcet's Disease (BD) is based on clinical criteria. Muco-cutaneous symptoms are the most important among them. Materials and Methods: From 1992 to 1999 we screened systematically all patients attending the Behcet's Disease Research Unit for muco cutaneous lesions. Only recurrent lesions were taken in consideration. Results: Mucous-membrane lesions: 1- Oral aphthosis was seen in 96.1%+ 0.6 of patients. The separation in major and minor aphthosis has no interest. There is no clear-cut separation between them. Oral giant aphthosis is very rare. In the same patient the intensity and the diameter of the lesions varied from one attack to another. 2- Genital aphthosis was seen in 63.9%+ 1.5 of patients. It is seen more often on the scrotum in males and on the vulva in females. Genital aphthosis is usually larger than oral aphthosis. Rarely the aphthous lesion can be seen around the anus. 3- Conjunctival aphthosis is very rare and ephemera. 4- Ulceration and erosion can be seen without any specific characteristic. 5- Erythema is seen around the aphthous lesions, but sometime it can be isolated. Skin Lesions were seen in 67.4% +1.5 of patients. Skin hyper sensibility to traumatism (pathergy) was frequent (59.9% + 1.6). Pseudo folliculitis is better be called Pustulosis. It is a vasculitis characterized by a dome shaped pustule on a round erythemato-edematous base. Sometimes it can be seen around hair follicles. Pustulosis is the most important cutaneous lesion of Behcet disease (65.5% +1.5). Small round erythemato-edematous lesions are characterized by a little round slightly painful weal on the skin without pustule in the center. Cutaneous aphthosis is rare but it is the most characteristic lesion of BD. It is seen on the inner side of the thigh, axilla, interdigital spaces, buttock, peri-anal skin and the trunk. Small nodules: They are very small and indurated painful dermic nodules. Behcet's cellulitis is a painful large round erythemato-edematous lesion. It has been mistaken in the past with Sweet syndrome. Subcutaneous lesions: They are better be named subcutaneous lesions of Behcet Disease instead of erythema nodosum. They are seen in 22.8% + 1.3 of patients. They are painful multiple subcutaneous nodules with different sizes. They have more often erythema and edema around the lesions than the classic erythema nodosum. Conclusion: Our study showed that mucocutaneous lesions of BD were numerous. While not specific of the disease, they had their own characteristic details. We propose to change the name of some of these lesions that were confusing and to have a better nomenclature to be closer to the reality.