The associations between serum ceruloplasmin level and the subsequent incidence of myocardial infarction and stroke were studied in a nested case-control study in Finland (baseline examination 1968-1972). Ceruloplasmin levels were measured in stored serum samples from 104 myocardial infarction or stroke cases occurring during a median follow-up of about 11 years and from 104 individually matched controls. High serum ceruloplasmin levels were significantly associated with higher future odds of myocardial infarction but not of stroke. The odds ratios for myocardial infarction and stroke comparing the highest and lowest tertiles of serum ceruloplasmin, adjusted for smoking, serum cholesterol, body mass index, hematocrit, hypertension, and diabetes, were 3.1 and 0.7, respectively. The results of the present study support the hypothesis that a high serum ceruloplasmin level is a risk factor for myocardial infarction.