The effects of guar incorporated into a complex spaghetti meal on the glycaemic response in 11 healthy and 6 non-insulin dependent diabetic (NIDDM) subjects was studied. To this end, subjects consumed spaghetti made of either Triticum aestivum or Triticum durum wheat with or without 20 g% guar, as part of a complex meal containing 27% fat, 19% protein and 51% carbohydrate. In both the healthy as well as the NIDDM subjects the incremental integrated postprandial glucose and C-peptide responses after ingestion of a guar spaghetti meal were not different from the values found after a spaghetti meal without guar. In NIDDM subjects the incremental glucose and C-peptide levels were lower at 60 and 90 min and 90 and 150 min respectively after ingestion of guar aestivum spaghetti. Our negative results of effects of guar on postprandial glucose values may be explained by the presence of normal quantities of fat and protein in the meal and imply that addition of dietary fibre to a complex meal is not useful in the dietary management of NIDDM.