We report two cases of paraneoplastic syndrome with sensory polyneuropathy. Case one showed numbness of the upper and lower extremities before a diagnosis of small cell carcinoma was made. Case two showed the same symptoms coincidentally with a recurrence of ovarian cancer. In both cases, Romberg's sign was positive, ataxic gait was noted, and the patient's skill movement was disturbed. Sensory nerve action potentials were not evoked in any of the nerves. Compound muscle action potential and motor conduction velocity were at the lower limits of normal. The neurological abnormalities did not resolve in spite of medical treatments. In these two cases, the loss of sensory neurons due to a lesion of the dorsal root ganglia was suggested. The loss of sensory feedback might lead to muscle weakness and fatigue, so they tend to be disused. For long-term rehabilitation management in these two cases, we suggested a regular exercise program to prevent muscle weakness.