Objective To test the hypothesis that diets with high glycaemic index (GI) and glycaemic load (GL) increase the risk of heart disease. Design Overall GI and GL were assessed from 7 d diet records or diet history interviews. Setting Information on hospitalization and death due to CVD and CHD was obtained from the National Register of Cause of Death and the National Register of Patients. Subjects In total 3959 adult Danes were – depending on time of entry – followed for 6–25 years until 31 December 1999. Results Overall GI was inversely associated with heart disease in men. The hazard ratios (95 % CI) for the 10th and 90th GI percentiles compared with the median were 1·38 (1·13, 1·68) and 0·90 (0·76, 1·07) for CVD morbidity, 1·45 (1·05, 1·99) and 0·81 (0·62, 1·06) for CVD mortality, and 1·31 (0·97, 1·76) and 0·65 (0·51, 0·84) for CHD morbidity. In male subjects GL was not associated with either outcome. In women no clear association between overall GI and heart disease was found, whereas positive non-linear associations were found for GL: at very high levels of GL, increase in GL was associated with increasing CVD and CHD morbidity. Conclusions In men low-GI diets were associated increased risk of heart disease and GL was not associated with heart disease. In women there was no clear association between GI and heart disease, but to some extent a positive association between GL and heart disease was observed as hypothesized.