The objective of this paper is to determine whether there is a relationship among obesity, gender, and the risk of development of primary spontaneous cerebrospinal fluid (CSF) rhinorrhea. A retrospective case review of all the patients with CSF rhinorrhea treated at our unit over a 10-year period is presented. From a series of 20 patients, we studied 9 cases of primary spontaneous CSF rhinorrhea; 6 patients were female (mean age 50 +/- 10 years) and 3 male (mean age 61 +/- 7 years). All the female patients were clinically obese, i.e., they had a body mass index >30 kg/m2. All the male patients had a body mass index within normal parameters. We review the postulated etiologic factors of this uncommon condition and study the pathophysiologic basis for obese patients to have CSF rhinorrhea. This study suggests a relationship between obese females and the risk of developing a primary spontaneous CSF rhinorrhea.