Diabetes is associated with abnormal autonomic function and increased mortality. Abnormal heart rate recovery after exercise, a measure of autonomic dysfunction, is also associated with increased mortality. The objective of this study was to determine the association of fasting plasma glucose with abnormal heart rate recovery and its prognostic importance in healthy adults. We studied 5,190 healthy adults who did not have medically treated diabetes (mean age 45 years, 39% women), were enrolled in the Lipid Research Clinics' Prevalence Study, and underwent exercise testing. Heart rate recovery was defined as the change from peak heart rate to that after 2 min of recovery; an abnormal value was < or = 42 bpm. All-cause mortality was assessed over 12 years. A total of 504 participants (10%) had impaired fasting glucose, and 131 (3%) had untreated diabetes. An abnormal heart rate recovery was found in 1,699 (33%). Compared with participants who had normal fasting plasma glucose, abnormal heart rate recovery was more common among those with impaired fasting glucose (42 vs. 31%; relative risk, 1.34; 95% confidence interval [CI], 1.20--1.50; P < 0.0001) and those with diabetes (50 vs. 31%; relative risk, 1.61; 95% CI, 1.35--1.92; P < 0.0001). Fasting plasma glucose remained an independent predictor of abnormal heart rate recovery even after adjustment for age, sex, and other confounders (P = 0.0003). An abnormal heart rate recovery added to impaired fasting plasma glucose for the prediction of death. Fasting plasma glucose is strongly and independently associated with abnormal heart rate recovery, even at nondiabetic levels.