Objectives: 1- Studying effectively of Plasma exchange in severe Guillain-Barre' syndrome. 2- Evaluation of complications of the Plasma exchange method. Subjects: From 1/2008 to 9/2010 we performed plasma exchange for 36 patients with severe Guillain-Barre' syndrome were treated at the intensive care department at Bach Mai Hospital with diagnosis of Guillain-Barre syndrome based on the standards of Asbury and comblath in 1990. Method: research progress with intervention studies, patients were evaluated according to the research protocol, the authors use fresh frozen plasma. Results: 36 patients (22 male, 14 female), average age 39.8 + or - 15.8 (15-72), 16 patients required artificial ventilation, plasma volume changes each time 35.6 + or - 5.43 (25.9 - 50.5 ml/kg), number of times for each patient was 4.9 + or - 1.3 on average (2-7 times). The patient's condition improved after each change plasma, but more slowly than patients with myasthenia gravis, some patients have recovered almost completely paralyzed muscles when the discharge, complications such as allergic reactions (rash, itching, red skin) accounted for 38/176 (21.6 percent) of the total number of episodes, there is a patient must stop plasma exchange as 1/2 times because of severe allergic rash no patient with anaphylactic shock, blood infection or local.The average hospitalization time is 16.3 + or - 11.1 (4 - 52 days). Conclusion: plasma exchange improved weak muscles condition of patients with Guillain-Barre syndrome, thereby shortening the time mechanical ventilation and hospitalization, limiting the complications caused by long lying. The most common complication is allergic reaction.