A review of epidemiological studies on the intake of oats and oat-based products and its effect on the risk of chronic disease and deaths was performed. Seven studies were identified of cancer risk (two each on prostate and colorectal cancer, and one each on pancreatic, breast and endometrial cancer), and one study on overall mortality. With the exception of a case-control study of pancreatic cancer, all studies were of cohort design: five studies were based on a single cohort from Denmark. The results of most cohort studies suggest a weak protective effect of a high intake of oats on cancer risk (relative risks in the order of 0·9). Potential limitations of the studies are dietary exposure misclassification, low statistical power because of limited exposure contrast and residual confounding. Despite the evidence from experimental and mechanistic studies of a protective effect of oats intake on CVD and diabetes, no epidemiological studies have been conducted on these conditions.