BACKGROUND: In observational studies, moderate drinking is associated with a reduced risk of more than twenty different diseases and health problems. However, it would be premature to conclude that there is a causal relationship. METHOD: This paper critically reviews the evidence for such associations. FINDINGS: It was found that reasons for questioning the causal association of moderate drinking and a reduced health risk are: the lack of dose-response relationships; the characteristics and lifestyles of today's abstainers and moderate drinkers; the lack of plausible biological mechanisms; the problems in the classification of drinking groups, and; the general limitations of observational studies. CONCLUSIONS: The evidence for the harmful effects of alcohol is undoubtedly stronger than the evidence for beneficial effects.