L1CAM is a member of the immunoglobulin gene superfamily of neural adhesion molecule. Abnormality of the L1CAM gene is associated with X-linked recessive form of congenital hydrocephalus (HSAS; hydrocephalus due to congenital stenosis of aqueduct of Sylvius) and some allelic disorders. Four new patients with congenital hydrocephalus consistent with the X-linked type were described. One of them had a novel mutation in the L1CAM gene.