Investigation of the relation between MEFV gene mutations and clinical findings of Beh double dagger et's disease. Genetic features of 100 patients with Beh double dagger et's disease (BD) and 100 healthy controls were analyzed. None of the individuals had a family history of FMF in the patient and control group, and none of the individuals in the control group had a family history of BD. MEFV gene analysis was performed in all the patients with BD and healthy controls; twelve different regions were scanned. In the BD group, mutations were detected in more than one region in 27 patients (27%). Twenty-five patients had heterozygous and two patients had compound heterozygous mutations (M680I-V726A and M694 V-A744S). The most frequent mutation was M694 V with an allelic frequency of 5%. The allelic frequencies of E148Q, M680I (G/C), and V726A were 3, 2, and 2%, respectively. The allelic frequencies of P369S, A744S, and K695R were 1, 1, and 0.5%. MEFV gene analysis revealed mutations in 27 (27%) of the individuals in the control group; the allelic frequency was 14%. The most frequent mutation was E148Q that was detected in 16 individuals. One individual was compound heterozygote (E148Q-M694 V). The allelic frequencies of E148Q, M694 V, V726A, and M680I were 8, 3, 1.5, and 0.5%, respectively. The allelic frequencies of K695R and P369S were 0.5 and 0.5%, respectively. The allelic frequency was similar in the two groups. There was not a significant relation between the mutations in the BD group and clinical findings.