In this paper, we propose an automatic method to segment the Sylvian fissure (SF) from T1-weighted Magnetic Resonance (MR) images. The method consists of four steps. First, morphological methods are applied to remove non-brain tissues. Then, 2D region growing is used to segment the cerebral spinal fluid (CSF) and gray matter (GM) in the SF, in which spatial relationships are used to control the region growing. A modified Fuzzy C-Means (FCM) clustering algorithm is introduced as well, which is more accurate than the conventional FCM method. After that, we get the 3D volume of the SF through segmenting CSF and GM slice by slice. Finally, CSF in the SF is extracted incorporating the anatomical information on a constant cortex thickness. We have demonstrated our method through both phantom and patient data.