Introduction - Experimental studies have demonstrated that mild hyperthermia exacerbates ischemia-induced neuronal injury. Material and methods - We examined the relationship between body temperature and functional outcome in 183 patients suffering from cerebral infarction, and admitted within 24 h from the onset of stroke. Patients’functional capacities in daily life were evaluated by Rankin's score before the attack (RS0), on the day of admission (RSI), and 3 months after the onset of stroke (RS90). Results - RS90 showed an independent correlation with RS0, RSI, age, infarct size and maximum body temperature recorded within the first 7 days from the onset of stroke by multivariate analysis. History of previous cerebrovascular accidents, atrial fibrillation, hemorrhagic transformation, infection, and a hypothalamic lesion showed significant associations with RS90 by the Mann-Whitney-test, but not by multivariate analysis. Infarct size correlated with body temperature, atrial fibrillation, and hemorrhagic transformation. Conclusion - Body temperature correlated well with both functional outcome and infarct size in patients with an acute cerebral infarction.