BACKGROUND The number of bariatric procedures is rapidly growing as the prevalence of obesity in the USA is increasing. Such procedures are not without complications, and those affecting the nervous system are often disabling and irreversible. We now describe our experience with these complications and review the pertinent literature. METHODS We describe 26 patients with major neurologic conditions that seemed causally related to bariatric surgery encountered in the neurology service of a tertiary referral university medical center over a decade. RESULTS The neurologic complications affected most regions of the nervous system: encephalopathy, optic neuropathy, myelopathy, polyradiculoneuropathy, and polyneuropathy. Myelopathy was the most frequent and disabling problem; symptoms began about a decade after surgery. Encephalopathy and polyradiculoneuropathy were acute and early complications. Except for vitamin B(12) and copper deficiencies in patients with myelopathy, we could not correlate specific nutritional deficiencies to the neurologic complications. All patients had multiple nutritional deficiencies, but their correction did not often yield dramatic results. The best result was achieved in one patient after surgical revision to reduce the bypassed jejunum. CONCLUSIONS A wide spectrum of serious neurologic conditions may follow bariatric surgery. These complications may occur acutely or decades later.