The aim of the study was to investigate the relation between insulin resistance and risk of cerebral infarction in a Japanese general population. The subjects were 2610 men and women without past history of stroke or myocardial infarction and who were under treatment for diabetes. Subjects were divided into quartiles by the homeostasis model assessment of insulin resistance (HOMA-IR), and Cox’s proportional hazard model was used to calculate hazard ratios (HRs) for cerebral infarction. In men, the multivariate-adjusted HRs were 2.51 (95% confidence interval [CI] = 0.98-6.42) in quartile 1 (Q1), 1.43 (95% CI = 0.54-3.82) in Q2, and 2.13 (95% CI = 0.82-5.51) in Q4, using Q3 as the reference. In women, the multivariate-adjusted HRs were 2.12 (95% CI = 0.72-6.31) in Q1, 2.96 (95% CI = 1.06-8.26) in Q3, and 2.31 (95% CI = 0.80-6.69) in Q4, using Q2 as the reference. The association between risk of cerebral infarction and HOMA-IR was not dose dependent.