Familial Mediterranean fever (FMF) and Behcet's disease (BD), both inflammatory diseases, are highly prevalent in the Middle Eastern and Mediterranean populations. FMF is a Mendelian autosomic recessive disease linked to MEFV, a gene of unknown function. BD in contrast is a polyfactorial disease associated with the major histocompatibility complex. Because FMF and BD have epidemiological similarities, we asked whether the FMF gene was implicated in BD. We screened for the common MEFV mutations a cohort of 114 chromosomes from definite BD patients [meeting the criteria of the International study group] and probable cases [meeting at least two of these criteria]. We screened in parallel an ethnically matched cohort of FMF and control chromosomes. The M694V, V726A and E148Q mutations tended to be more frequent in definite BD (2.6%, 2.6%, and 5.2%, respectively) than in controls (0%, 0%, and 2.2%). The P706 polymorphism was found in 10.5% of the probable BD chromosomes, but in only 1.6% of the controls (p=0.01). Because some MEFV mutations were more frequent in BD than in controls, we suggest that they may act as additional susceptibility factors in BD. (C) 2000 Wiley-Liss, Inc.