A 69-year-old woman presented with subacute sensory neuropathy and autonomic dysfunction of 9 months' duration, associated with high serum titers of anti-Hu antibodies. A small cell carcinoma of the lung was diagnosed by biopsy. She died after cardiorespiratory arrest. At autopsy, spinal and autonomic ganglia showed subacute inflammation with diffuse endoneurial T-cell, B-cell, and plasma cell infiltration. The cytoplasm and nuclei of some ganglion neurons displayed IgG immunocytochemical positivity. CD8+ T cells were tightly attached to, and indented the cell surface of, IgG-positive and IgG-negative neurons. This observation suggests that both cytotoxic T-cell-mediated attack against neurons and humoral mechanisms play a role in paraneoplastic subacute sensory neuronopathy.