The presence of inexcitable motor nerves early in the course of Guillain-Barré syndrome (GBS) identifies a subgroup of patients with more severe disease and delayed recovery. How frequently these electrodiagnostic findings reflect a primary axonal attack ("axonal" GBS) is controversial. We present two children with severe acute GBS, delayed recovery, and residual disability despite early treatment with human immunoglobulin. They had inexcitable motor nerves at days 6 and 7, and profuse fibrillations and positive waves on subsequent studies. Clinically and electrodiagnostically, both children's disease resembled the acute motor-sensory axonal variant of GBS (AMSAN). Sensory and motor nerve biopsies revealed severe macrophage-associated demyelination with axonal degeneration of variable severity. We conclude that clinical and electrodiagnostic features cannot discriminate between the "axonal" and demyelinating GBS. Early and severe demyelination with secondary axonal damage may mimic clinically and electrophysiologically the AMSAN variant of GBS.