The purpose of this study was to prospectively evaluate the combined effects of hypertension and heart rate on the risk of stroke and coronary heart disease (CHD) among Inner Mongolians. Based a cross-sectional survey in 2002-2003, a prospective cohort study was conducted among 2530 Mongolian people. We categorized the participants into four subgroups according to blood pressure and heart rate. Cox proportional hazards models and receiver operating characteristic (ROC) curves were used to evaluate the association between hypertension, heart rate, and stroke and CHD incidence. During the follow-up period, a total of 120 stroke and 75 CHD patients were observed. Compared with normotensives with a heart rate <80 b.p.m., in a multivariate-adjusted model, the hazard ratios (HRs; 95% confidence intervals (CIs)) of stroke for hypertensives with a heart rate <80 b.p.m. and hypertensives with heart rate ⩾80 b.p.m. were 3.21 (1.80-5.70) and 3.59 (1.95-6.62), respectively (all P<0.05); the HRs (95% CI) of CHD for hypertensives with a heart rate <80 b.p.m. and hypertensives with a heart rate ⩾80 b.p.m. were 2.09 (1.07-4.07) and 2.76 (1.43-5.36), respectively (all P<0.05). For both stroke and CHD incidence, the area under ROC curve for a model containing hypertension and a heart rate ⩾80 b.p.m. along with other conventional factors was significantly larger than the one containing only other conventional factors (all P<0.05). Hypertensives with a high heart rate had the highest risk of stroke and CHD among the Inner Mongolians. These results indicate that the coexistence of hypertension and high heart rate may be a valuable predictor of stroke and CHD incidence.