Objective: Dietary glycemic index (GI) and glycemic load (GL), measures of the propensity of dietary carbohydrate to increase blood glucose, have been associated with risk of coronary heart disease, but their association with incidence of heart failure (HF) is unknown. The authors therefore assessed whether dietary GI and GL were associated with rates of HF events. Methods: The authors conducted a prospective, observational study of 36,019 women 48–83 years old without baseline HF, diabetes, or myocardial infarction who were participants in the Swedish Mammography Cohort, a prospective cohort study. Diet was measured using food-frequency questionnaires. Women were followed from January 1, 1998, through December 31, 2006, for HF hospitalization or death through the Swedish inpatient and cause-of-death registers. Cox proportional hazards models adjusted for age and other risk factors were used to estimate incidence rate ratios (RRs) and 95% confidence intervals (CIs). Results: Over 9 years of follow-up, 639 of 36,019 women died of HF (n = 54) or were hospitalized for HF for the first time (n = 585). The authors did not find statistically significant associations between dietary GI and HF events (RR comparing highest to lowest quartile = 1.12, 95% CI = 0.87–1.45, p for trend = 0.31) or between dietary GL and HF events (RR comparing highest to lowest quartile = 1.30, 95% CI = 0.87–1.93, p for trend = 0.16). Results were not significantly different in normal weight and overweight women. Conclusions: In this population, dietary GI did not appear to be associated with incident HF events. There was a suggestion of an association between dietary GL and HF, which did not reach statistical significance. © 2009 American College of Nutrition.