The results of four randomized controlled trials were examined to assess the efficacy of intravenous immunoglobulin (IVIG) for myasthenia gravis (MG) acute exacerbations. The first trial compared plasma exchange (PE) and IVIG in 87 patients. At day 15, the mean change in the Myasthenic Muscular Score (MMS) was 16.6 (95% CI 11.6-21.6) in the PE group and 15.6 (95% CI 10.9-20.3) in the IVIG group (Wilcoxon signed rank test, P = 0.65). The second trial compared IVIG to oral methylprednisolone, and 33 patients were included. The mean (SD) sum of the two most pathological items of the Quantitative Myasthenia Gravis Score (QMGS) at day 0 was 3.9 (1.1) for the IVIG group and 4.2 (0.7) for the methylprednisolone group. At day 14, these values were 2.9 (1.4) for the IVIG group and 2.8 (1.1) for the methylprednisolone group. The third trial compared IVIG 2 g/kg versus placebo for MG worsening. The mean change in QMGS at day 14 was -2.54 in the IVIG group and -0.89 in the placebo group (P = 0.047). A significant IVIG treatment effect was observed only in patients with more severe disease; the mean difference was -0.10 for mild MG (P = 0.914) and -3.39 for moderate to severe MG (P = 0.010). The last trial compared IGIV 2 g/kg versus 1 g/kg for MG acute exacerbation in 173 patients. The mean MMS change in both groups was similar (difference = 3.84; 95% CI -1.03 to 8.71; P = 0.12). In conclusion, IVIG may be used as treatment for MG acute exacerbations. IVIG at a dose of 1 g/kg may be sufficient.