Anti-Hu-associated paraneoplastic sensory neuropathy (PSN) has been reported to be nonresponsive to immunotherapy or cancer therapy. We report 2 patients with anti-Hu-associated PSN who achieved sustained clinical improvement with early and aggressive immunotherapy 10-15 months before the diagnosis of small-cell lung carcinoma. Both had chronic "sensory neuronopathy plus"; in addition to sensory neuronopathy, case 1 had a motor-autonomic dysfunction with encephalopathy, and case 2 had a motor-autonomic dysfunction with swallowing difficulty. These two cases were unusual in that sustained clinical improvement was achieved with early aggressive immunotherapy before the detection of cancer and without any concomitant anticancer therapy or lowering of anti-Hu antibody titer. We believe that early and aggressive immunotherapy should be tried in any patient with anti-Hu-associated PSN, as it may induce sustained clinical improvement.