Interleukin (IL)-18 is a novel proinflammatory cytokine that plays a central role in innate and acquired immunity, making it a likely inflammatory candidate in atherosclerosis. We investigated whether circulating IL-18 levels were associated with subclinical atherosclerosis in a community population. Carotid intimal medial thickness (IMT) and carotid plaques were assessed in a cross-sectional study of 1111 randomly selected community subjects, aged 27-77 years. Baseline levels of IL-18, IL-6, high sensitive CRP (hsCRP), fibrinogen and white cell counts were measured along with conventional cardiovascular risk factors. Men had higher mean IL-18 levels than women (P<0.0001). Spearman rank correlations (r(s)) showed that IL-18 was weakly correlated with all inflammatory markers in the whole population (r(s) between 0.11 and 0.23, all P<0.001). IL-18 was also correlated with conventional risk factors including waist-hip ratio, BMI, blood pressure, triglycerides, HDL (inversely) and pack-years smoking (r(s) between 0.18 and 0.39, all P<0.001) but not with LDL-cholesterol. Independent predictors of IL-18 concentrations were waist-hip ratio, HDL, IL-6, hsCRP and hypertension. There was a positive univariate association of IL-18 levels with carotid IMT (P<0.001) and plaque prevalence (P<0.001) but no residual association after adjustment for conventional risk factors (both P>0.05). In a cross-sectional community population, IL-18 levels were related to traditional risk factors and inflammatory markers but were not independently associated with subclinical carotid atherosclerosis.