Cerebrospinal fluid IGG and the relations with total proteín, and with prealbumin + albumin and the IGG index were studied in 160 patients with various neurological disorders. These patients were distributed in 8 groups according to diagnosis as follows: inflammatory (21 cases); demyelinating (31 cases); degenerative (10 cases); cerebrovascular (19 cases); tumoral (3 cases); convulsive (20 cases); headache (11 cases); other neurological disorders (45 cases). According to the results (table 1) the best aplicability of IGG study is the group of chronic inflammatory diseases (neurosyphilis and neurocysticercosis) and the demyelinating disorders (multiple sclerosis). Emphasis is given to the possibility of the occurrence of local synthesis of IGG in the central nervous system in these 2 groups.