Elevated levels of C reactive protein (CRP) are associated with increased risk of ischaemic vascular disease. We tested whether this is a causal association. CRP > 3 vs < 1 mg/l were associated with an increased risk of ischaemic heart- and cerebrovascular disease of 1.6 and 1.3, respectively. Four CRP polymorphisms were associated with a 64% increase in CRP levels, resulting in a theoretically predicted increased risk of 32% and 25% for ischemic heart- and ischemic cerebrovascular disease, respectively. However, these genotype combinations were not associated with an increased risk of ischaemic vascular disease.