It is well known that vitamin E acts as a useful preventive agent against several types of cancers and stroke. However, there are conflicting results on a role of vitamin E in the prevention of these diseases. In order to clarify the conflicting results, meta-analysis of current results obtained from randomized controlled trials (RCTs) was conducted. Meta-analysis of 7 RCTs on cancer identified showed no significant difference on the effect of vitamin E supplementation on incidence and mortality in cancers tested. However, there was heterogeneity in the meta-analysis of prostate cancer incidence, indicating the possibility that vitamin E supplementation has a suppressive effect against the cancer in some cases. With respect to incidence and mortality in stroke, meta-analysis of 6 RCTs identified was conducted, and vitamin E supplementation significantly reduced the incidence of ischemic stroke, but not hemorrhagic stroke. Thus, it is suggested that vitamin E supplementation has a preventive effect on ischemic stroke.