Employing a nested case-control design, baseline plasma samples are assayed for four markers of inflammation (interleukin-6, TNF-alpha, soluble ICAM, soluble VCAM) and four markers of chronic infection (antibody titers directed against Chlamydia pneumoniae, Helicobacter pylori, Herpes simplex virus, and cytomegalovirus). Case subjects are those study participants who have subsequently developed MI (N=550), CVA (N=400), or VTE (N=200). Control subjects are selected from those study participants who remained healthy during follow-up and are matched to the cases by age, smoking status, and follow-up time. Data on usual cardiovascular risk factors, lipid parameters, and hemostatic markers of risk are already available in the PHS and will be used to evaluate the results for potential confounding and effect modification. Since the PHS was a randomized trial of low-dose aspirin for its initial 5 years, this cohort also provides the unique opportunity to investigate whether the use of an agent with anti-inflammatory properties modifies the risk of subsequent thrombosis among those with underlying inflammation. Indeed, this intriguing hypothesis has recently been raised regarding data relating another marker of inflammation, C-reactive protein, to future risks of myocardial infarction and stroke.