A neuropsychiatric syndrome developed in four patients 2 1/2-9 months after gastric partition for morbid obesity. Since the partition, all four patients had recurrent severe vomiting with severe weight loss (52 to 100 lb) and they had not had vitamin supplementation. Two patients had peripheral neuropathy along with confusion and memory loss of recent events. The other two had peripheral neuropathy alone. Vitamin B complex replacement was especially helpful in the management of these patients. Peripheral neuropathy completely resolved in one of the patients, whereas the other three patients were left with residual weakness in their extremities and two had recent memory loss. Awareness of this complication may result in early recognition and treatment in the postgastric partition patient.