OBJECTIVE To examine the relationship between alcohol consumption and risk of mortality and incident coronary heart disease (CHD), taking account of variation in intake during follow-up. METHODS Prospective cohort study of 5411 male civil servants aged 35-55 years at entry to the Whitehall II study in 1985-88. Alcohol consumption was reported five times over a 15-year period. Mortality, fatal CHD, clinically verified incident non-fatal myocardial infarction and definite angina were ascertained during follow-up. RESULTS We found evidence that drinkers who vary their intake during follow-up, regardless of average level, have increased risk of total mortality (hazard ratio of high versus low variability 1.52: 95% CI: 1.07-2.17), but not of incident CHD. Using average consumption level, as opposed to only a baseline measure, gave slightly higher risk estimates for CHD compared to moderate drinkers at the extremes of the drinking range. CONCLUSIONS Multiple repeated measures are required to explore the effects of variation in exposure over time. Caution is needed when interpreting risks of exposures measured only once at baseline, without consideration of changes over time.