The primary aim of the present study was to expand the glycaemic index (GI) database by determining the GI and insulin index values of thirty-nine foods containing sugars in healthy adults. The second aim was to examine the hypothesis that glycaemic and insulin responses to foods which contain added sugar(s) are higher than responses to foods containing naturally-occurring sugars. Eight healthy subjects drawn from a pool of eighteen consumed 50 g carbohydrate portions (except 25 g carbohydrate portions for fruits) of the test foods. The GI and insulin index were determined according to standardized methodology and expressed on a scale on which glucose = 100. The median GI and insulin index values of all foods tested were 56 (range 14 to 80) and 56 (range 24 to 124) respectively. The median GI of the foods containing added sugars was similar to that of foods containing naturally-occurring sugars (58 v. 53 respectively, P = 0·08). Likewise, the median insulin index of the foods containing added sugars was not significantly different from that of foods containing naturally-occurring sugars (61 v. 56 respectively, P = 0·16). There was no evidence of‘rebound hypoglycaemia’or excessive insulin secretion relative to the glucose response. We conclude that most foods containing sugars do not have a high GI. In addition, there is often no difference in responses between foods containing added sugars and those containing naturally-occurring sugars.