In most carbohydrate-containing foods, the blood insulin response is predictable and is closely linked to the food's glycaemic index (GI). A single study, examining whole milk and fermented milk products made from whole milk, recently reported a large dissociation between the GI and insulinaemic index (II) in healthy normal adults. Because the fat component of a food may influence the GI and II, it is unclear if a similar dissociation may exist for skimmed milk in normal adults. We determined the GI and II of both skimmed and whole milk in nine healthy, male (n 6) and female (n 3) subjects (23·6 (sd 1·4) years). No significant (P>0·05) differences existed between GI and II for skimmed and whole milks. Significant (P<0·05) differences were observed between the actual and predicted areas under the insulin curves for both skimmed milk (predicted 1405 (sd 289) pmol×min/l; actual 6152 (sd 1177) pmol×min/l) and whole milk (predicted 1564 (sd 339) pmol×min/l; actual 5939 (sd 1095) pmol×min/l). Consequently, a large and similar dissociation of the GI and II existed for both whole milk (42 (sd 5) and 148 (sd 14)) and skimmed milk (37 (sd 9) and 140 (sd 13)). It is concluded that the dissociation of the GI and II in milk is not related to its fat content.