We investigated the effect of elevated concentrations of fasting plasma glucose (FPG) or hemoglobin A1c (HbA1c) on the risk of development of hypertension among apparently healthy Japanese. Studied were 9584 individuals without known diabetes and hypertension. During a 5-year follow-up period, 1098 individuals developed hypertension. Elevated concentrations of FPG, rather than of HbA1c, were significantly predictive of future hypertension. Compared with the lowest quartile category of FPG (&lt
4.9 mmol l-1), the second (4.9-&lt
5.2 mmol l-1), third (5.2-&lt
5.6 mmol l-1) and highest (≥ 5.6 mmol l-1) quartile categories had age-, sex- and body mass index-adjusted odds ratios (95% confidence interval) of 1.35 (1.10, 1.66), 1.39 (1.13, 1.71) and 1.85 (1.51, 2.28) for hypertension, respectively. In the highest quartile of FPG, the multivariate-adjusted OR was 1.37 (1.10, 1.70) compared with the lowest quartile. Results of these adjusted models showed no significant association across quartile categories of HbA1c concentrations and an increased risk of developing hypertension. The joint effect of hyperglycemia and overweight, older age or prehypertension resulted in further elevated ORs for hypertension than the absence of such an association. Higher FPG levels rather than HbA1c were strongly predictive of future hypertension among Japanese. Hyperglycemia along with older age, overweight and prehypertension contributed to identifying individuals at increased risk of developing hypertension.