IgG-Alb ratio, IgG index and IgG synthesis rate were determined in 40 patients with multiple sclerosis (MS group), 20 patients with other neurologic diseases (OND group) and 22 normal persons (normal group) by using Beckman Immunochemistry System II. The results showed the average values and abnormal frequencies of the three parameters in MS group were significantly higher than those in the normal group and OND group (P less than 0.01), indicating the synthesis of IgG within the central nervous system (CNS) in MS. These parameters were increased in most of the MS patients. Therefore, they could be used in the diagnosis of MS. It was also found that the amount of IgG synthesized within CNS was decreased in patients treated with corticosteroids.