A case of paraneoplastic encephalomyelitis and subacute pandysautonomia associated with an occult atypical carcinoid tumour of the lung is described. The main clinical features were lethargy, impaired memory, constipation, and orthostatic hypotension. Neurological investigation was unremarkable except for mononuclear pleocytosis and increased protein level in the cerebrospinal fluid (CSF). Tests of autonomic function revealed a low plasma norepinephrine level, a marked drop of blood pressure (BP) to vertical tilt and Valsalva maneuver, and a marked rise of BP to dilute norepinephrine infusion. A few days prior to death, the patient became hypothermic and had repeated episodes of respiratory arrest associated with transient atrioventricular block on the electrocardiogram (ECG). A polysomnographic study confirmed a sleep apnea syndrome. Autopsy revealed an atypical carcinoid tumour in one tracheobronchial lymph node, widespread lymphocytic infiltrates and loss of neurons in the cerebral, cerebellar and brainstem grey matter, the spinal cord and roots, and the paravertebral sympathetic ganglia as well as microglial and astrocytic proliferation in the central nervous system.