Although there is no designated laboratory profile for diagnosing Behçet’s disease (BD), the crucial factor lies in carrying out a comprehensive history, reviewing symptoms, and conducting detailed physical examinations. BD manifests a heterogeneous pattern of organ involvement occurring in recurrent episodes. Defining disease activity in BD is challenging due to its fluctuating course, the absence of laboratory tests reflecting overall disease activity, and the lack of standardized forms for reporting the severity of its manifestations. Currently, there are no laboratory markers that demonstrate a strong correlation with clinical activity in BD. Consequently, several disease activity indexes have been developed. In order for a measurement of disease activity to be useful, it needs to meet three key criteria: validity, reliability, and simplicity for routine clinical use. This chapter specifically examines the activity scales that are commonly employed to assess disease activity in BD.