There is evidence that proinflammation may be linked to the development of hypertension (HT). We examined the association of both the interleukin-1 beta (IL-1beta) and the interleukin 1-receptor antagonist (IL-1ra) with future blood pressure (BP) and HT occurrence (BP >or= 140/90 mmHg, or antihypertensive drug) in a population-based prospective study. Our study consisted of 396 (147 men and 249 women) middle-aged, baseline apparently healthy, normotensive subjects participating in a 6.5-year follow-up study. Subjects with high-sensitivity CRP (hs-CRP) < 10 mg/L were excluded at the initial visit. At follow-up, the occurrence of HT was 32%. The levels of baseline IL-1beta and IL-1ra were significantly higher for subjects who developed HT during the follow-up than for those who did not (IL-1beta; 0.67 +/- 0.62 pg/mL versus 0.56 +/- 0.32 pg/mL, P = .020 and IL-1ra; 184 +/- 132 pg/mL versus 154 +/- 89 pg/mL, P = .007). After adjustments for age, follow-up time, sex, baseline systolic BP, and BMI, our results confirm a statistically significant (P = .036) linear association between the quartiles of IL-1beta and change of systolic BP during the study. After adjustments for age, follow-up time, sex, and BMI, our results also show a linear association between incident HT and the quartiles of IL-1ra. (P = .026). These results provide evidence that proinflammation may precede BP elevation and HT.