Behcet’s Disease (BD) is a chronic inflammatory multisystem disease belongs to the Vasculitidies with small, medium and large sized vessel involvement. This disorder is 
characterized by Oral aphthosis, Genital aphthosis, ocular inflammation, skin lesions, vascular involvement, positive Pathergy test and HLA-B51 positivity. When a patient is involved in Behcet’s Disease (BD) but his/her disease is presented as simple oral aphthosis and in which the pathergy test and/or HLA-B51 are positive but other clinical features are obscured; it is called subclinical BD. Two types of subclinical BD have been detected by the author yet; type I and type II. 

Subclinical BD type I is a varient of BD with the combination of: 
• Low frequent, minor, recurrent oral aphthosis 
• Occasionally a few pseudofolliculitis lesions and 
• The pathergy test and/or HLA-B51 positivity Subclinical BD type II is a varient of BD with the combination of: 
• Low frequent, minor, recurrent oral aphthosis 
• Recurrent internal genital (vaginal/cervical) aphthosis and 
• The pathergy test and/or HLA-B51 positivity Indeed some parts of the cases with simple oral aphthosis are the cases with missed subclinical BD. So, the author thinks that, the prevalence of BD may be underestimated. 
 
 
Keywords: Oral Aphthosis; Genital Aphthosis; HLA-B51 Positivity; Pathergy Test; Subclinical BD Type I and II