Ten cases of small intestinal obstruction seen over a period of 6 years (1971-6) in young girls within the narrow age range of 13-18 years are described. The patients were all within 2 years of menarche. In all these cases the obstruction was due to a membrane encasing the small intestine in the manner of a cocoon. There was no previous history of abdominal operation, peritonitis or prolonged drug intake. The clinical features, operative findings and management of the cases are presented. Possible causes of the condition are discussed. In view of the similar clinical presentation in all these patients, their conditions can be grouped as a clinical entity--'the abdominal cocoon'.