AIMS: The prediction of future heart failure (HF) in stable outpatients is often difficult for general practitioners and cardiologists. Recently, the H2 FPEF score (0-9 points) has been proposed for the discrimination of HF with preserved ejection fraction from non-cardiac causes of dyspnoea. The six clinical and echocardiographic variables that constitute the H2 FPEF score include the following: (i) obesity (H); (ii) the use of ≥2 antihypertensive drugs (H); (iii) atrial fibrillation (F); (iv) pulmonary hypertension (P); (v) an age > 60 years (E); and (vi) E/e' > 9 (F). We performed an external validation study that investigated whether the H2 FPEF score could predict future HF-related events in stable outpatients with cardiovascular risk factor(s) in Japan. METHODS AND RESULTS: In this prospective cohort study, after exclusion of 195 from 551 consecutive, stable Japanese outpatients with at least one cardiovascular risk factor who were enrolled between September 2010 and July 2013, the remaining 356 outpatients (171 men, 185 women, mean age 73.2 years) were eligible for the analysis. We calculated the H2 FPEF score (0-9 points), and followed up the patients for an average of 517 days. In all of the 356 patients, the mean H2 FPEF score was 3.1 ± 1.8, and 15 developed HF-related events during the follow-up period, including cardiovascular death (n = 2) and hospitalization for HF decompensation (n = 13). Multivariate Cox proportional hazards analysis showed that the H2 FPEF score was an independent predictor of future HF-related events (P < 0.001 for all three models). Kaplan-Meier survival curves showed a significantly higher probability of HF-related events in the outpatients with a high H2 FPEF score (P < 0.001). In receiver operating characteristic (ROC) curve analysis, the H2 FPEF score was significantly associated with the occurrence of future HF-related events (P < 0.001). In ROC curve analysis, the sensitivity, specificity, and positive likelihood ratio of a H2 FPEF score of 7 points to predict HF-related events were 47%, 96%, and 11.4%, respectively. CONCLUSIONS: The H2 FPEF score could provide useful information for future HF-related events in stable outpatients with cardiovascular risk factor(s) in Japan.