Background: Multifocal motor neuropathy with conduction blocks (MMNCB) is an i mmune mediated motor neuropathy. Previous long term IV immunoglobulin (IVIg) t reatment studies have documented improvement in muscle strength and functional d isability but revealed a concomitant increase in acute axonal degeneration (AD) and conduction block (B). Objective: To determine the long term effects of IVIg therapy on clinical and neurophysiologic outcome measures in MMNCB patients res ponsive to IVIg. Methods: The authors reviewed medical records of 10 patients wi th MMNCB for outcomes in muscle strength (Medical Research Council score), funct ional disability (Modified Rankin Disability score), CB, and AD. All patients ha d received IVIg (2g/kg in 5 days for 3 consecutive months), followed by monthly maintenance therapy. Results: Patients were followed for an average of 7.25 year s (range, 3.5 to 12 years). There was significant and sustained improvement in m uscle strength and functional disability while on IVIg therapy. Furthermore, the authors found significant improvement in CB, decrease in AD, and evidence of re innervation by the end of the follow up period. Conclusion: Long term IV immun oglobulin therapy improves muscle strength and functional disability, decreases the number of conduction blocks and the extent of axonal degeneration, and promo tes reinnervation. These findings differ from previous reports of deterioration in neurophysiologic outcome measures. Comparison of the IV immunoglobulin regime n in those reports and this study shows that the authorspatients were treated with significantly higher IV immunoglobulin maintenance doses. These findings ha ve implications for the long term treatment of patients with multifocal motor n europathy with conduction blocks. Background: Multifocal motor neuropathy with conduction blocks (MMNCB) is an i mmune mediated motor neuropathy. Previous long term IV immunoglobulin (IVIg) t reatment studies have documented improvement in muscle strength and functional d isability but revealed a concomitant increase in acute axonal degeneration ( AD) and conduction block (B). Objective: To determine the long term effects of IVIg therapy on clinical and neurophysiologic outcome measures in MMNCB patients res ponsive to IVIg. Methods: The authors reviewed medical records of 10 patients wi th MMNCB for outcomes in muscle strength (Medical Research Council score), functional disability (Modified Rankin Disability score), CB, and AD. All patients ha received IVIg (2g / kg in 5 days for 3 consecutive months), followed by monthly maintenance therapy. : Patients were followed for an average of 7.25 year s (range, 3.5 to 12 years). There was significant and sustained improvement in m uscle strength and functional disabi Further, the authors found significant improvement in CB, decrease in AD, and evidence of re innervation by the end of the follow up period. Conclusion: Long term IV immunoglobulin therapy improves muscle strength and functional disability, the number of conduction blocks and the extent of axonal degeneration, and promo tes reinnervation. These differences differ from previous reports of deterioration in neurophysiologic outcome measures. Comparison of the IV immunoglobulin regime n in those reports and this study shows that the authors patients were treated with significantly higher IV immunoglobulin maintenance doses. These findings ha ve implications for the long term treatment of patients with multifocal motor n europathy with conduction blocks.