Abstract: Introduction: Behcet's Disease (BD) is characterized by recurrent attacks and remissions, making difficult the assessment of the treatment's result. Moreover, the remission period between the attacks is not the same and may vary from one attack to another. The attack periods are not always the same and may vary in severity, or extent of organ involvement. Iran Behcet's Disease Dynamic Activity Measure (IBDDAM) takes in account all of these parameters and calculates a mean disease activity index per month. The aim of this study was to validate IBDDAM with The Physician Global Assessment (PGA) in a patients cohort in the evaluation of treatment results. Method: Ninety-six patients with BD were followed prospectively, regardless of their treatment modalities. The range of follow-up was from 3 to 32 months. Results: Patients were divided in 3 groups according to their PGA: 1.The PGA showed no change in the disease activity in 62 (65%) patients during the study. In this group of patients, IBDDAM remained unchanged in 49 of them (79%), increased in 7 (11%), and decreased in 6 (10%) of them. In this group of 62 patients and according to their disease activity two groups were characterized, those who had an active disease and those who were in remission. Twenty four patients were in the active group; IBDDAM did not change in 16 of them (67%), improved in 5 of them (21%) and aggravated in 3 (12%). Thirty-eight patients were in the remission group; IBDDAM showed no change in 33 of them (87%), improved in 1 (3%) and aggravated in 4 (10%) of them. The accordance of PGA and IBDDAM for the Active Disease Group and the Remission group was different. The difference was statistically significant (x2=4.933, p=<0.03). 2.The PGA showed an aggravation in 9 patients; the IBDDAM showed the same. 3.The PGA showed an improvement in 25 patients; in 23(92%) of them IBDDAM improved too, and in 2 patients (8%) it remained unchanged. The IBDDAM change agreed in 84% of cases with PGA. Conclusion: IBDDAM is a reliable index for the evaluation of the treatment in BD.