Few previous studies in Western populations have reported an association between C-reactive protein (CRP) and prehypertension. However, no previous study has examined this association in Asians. We examined individuals who were free of hypertension from two independent population-based studies in Singapore: the Singapore Prospective Study Programme (SP2, n=2843 Chinese, Malay and Indians aged 24 years) and the Singapore Malay Eye Study (SiMES, n=957 Malays, aged 40-80 years). Prehypertension was defined as systolic blood pressure (BP) 120-139 mm Hg or diastolic BP 80-89 mm Hg. CRP was analyzed as categories (<1, 1-3, >3 mg l(-1)). The prevalence of prehypertension increased with increasing categories of CRP in both cohorts (P for trend <0.05 in both cohorts). After adjusting for potential confounders including body mass index (BMI), smoking and diabetes, persons with higher levels of CRP were more likely to have prehypertension in both SP2 (compared with CRP <1 mg l(-1), odds ratio (OR) 1.23, 95% confidence interval (CI) 1.03-1.48 for CRP 1-3 and OR 1.67, 95% CI 1.32-2.10 for >3 mg l(-1)) and SiMES (OR 1.45, 95% CI 1.04-2.01 and OR 1.56, 95% CI 1.07-2.27) respectively. In conclusion, data from two population-based Asian cohorts suggest that elevated serum CRP levels are associated with prehypertension.