Ingestion of 5 g guar gum (Glucotard) led to complete obstruction of the distal oesophagus in a 63-year-old diabetic. A daily intake of 5 g guar gum t.i.d. with 250 ml of water had been tolerated without problems for half a year. Intake of a sufficient amount of water, as well as an undisturbed oesophageal function, are absolutely essential for the ingestion of guar gum. Since alcohol can influence the process of swelling and the consistency of the bolus, simultaneous intake of alcohol and guar gum should be strictly avoided.