A prospective study of the clinical evolution of 78 patients diagnosed of mediterranean botonous fever has been performed. Hospital admissions because of complications were necessary in 5 (6,4%) patients. 13 patients (16,6%) had a devious evolution with signs of severe involvement of organs and systems. The evolution was favorable in the remaining 60 cases (79,9%) on home treatment with doxycycline. The unfavorable evolution was associated with advanced age, underlaying chronic disease, and the delay in the initiation of the appropriate treatment. Previous thrombopenia was the major predictive biological factor of unfavourable evolution in our patients.