The diagnosis of certain metabolic diseases is problematic because it cannot be achieved with conventional blood and urine analyses but requires cerebrospinal fluid (CSF) study. CSF analysis is essential for the diagnosis of neurotransmitter metabolic disorders (synthesis defects of biogenic monoamines, non ketotic hyperglycinemia and homocarsinosis), defects of specific transporters (glucose cerebral transporter (Glut1) deficiency and cerebral folate deficiency) and is of help for the diagnosis of disorders of cerebral energy metabolism (respiratory chain disorders and pyruvate dehydrogenase deficiency). Our goal is to give an outline of hereditary metabolic diseases whose diagnosis is based on CSF analysis. We will detail late onset clinical forms which may be first seen in an adult neurology department.