BACKGROUND: Noninvasive assessment of intima-media thickness (IMT) is widely used in observational studies and trials as an intermediate or proxy end point for cardiovascular disease. However, data showing that IMT predicts cardiovascular disease are limited. We studied whether common carotid IMT is related to future stroke and myocardial infarction. METHODS AND RESULTS: We used a nested case-control approach among 7983 subjects aged > or =55 years participating in the Rotterdam Study. At baseline (March 1990 through July 1993), ultrasound images of the common carotid artery were stored on videotape. Determination of incident myocardial infarction and stroke was predominantly based on hospital discharge records. Analysis (logistic regression) was based on 98 myocardial infarctions and 95 strokes that were registered before December 31, 1994. IMT was measured from videotape for all case subjects and a sample of 1373 subjects who remained free from myocardial infarction and stroke during follow-up. The mean duration of follow-up was 2.7 years. Results were adjusted for age and sex. Stroke risk increased gradually with increasing IMT. The odds ratio for stroke per standard deviation increase (0.163 mm) was 1.41 (95% CI, 1.25 to 1.82). For myocardial infarction, an odds ratio of 1.43 (95% CI, 1.16 to 1.78) was found. When subjects with a previous myocardial infarction or stroke were excluded, odds ratios were 1.57 (95% CI, 1.27 to 1.94) for stroke and 1.51 (95% CI, 1.18 to 1.92) for myocardial infarction. Additional adjustment for several cardiovascular risk factors attenuated these associations: 1.34 (95% CI, 1.08 to 1.67) and 1.25 (95% CI, 0.98 to 1.58), respectively. CONCLUSIONS: The present study, based on a short follow-up period, provides evidence that an increased common carotid IMT is associated with future cerebrovascular and cardiovascular events.