Dietary fibre may retard glucose absorption in normal and diabetic subjects. It is, however, unclear which type of fibre would be most suitable for this purpose. We therefore studied whether pectin differs from fibre from barley (85%) and citrus (15%) (Dumovital) in its effect on postprandial blood glucose responses. Eight insulin-dependent diabetics fasted overnight and were then given a meal without their morning insulin. The basic meal, composed of 90 g white bread and 120 g jam (total carbohydrate 105 g), was given three times: alone, with 15 g pectin and with 15 g Dumovital fibre. Blood glucose was measured for three hours. The tests showed that pectin administration considerably inhibited the postprandial rise in blood glucose, while Dumovital showed no such effect. Barley/citrus fibre (a mixture of cellulose, hemicellulose, lignin and pectin) has not the same inhibiting effect on postprandial rise in blood glucose as pure pectin in insulin-dependent diabetics. Thus, the specific type of fibre must be considered when prescribing dietary fibre to diabetics.