OBJECTIVE Alcohol drinkers are generally considered to underreport their alcohol intake, but little is known about whether they correctly report their energy intake (EI). We assessed the validity of the reported energy intake of alcohol drinkers using the 24-hour urinary (U) excretion of potassium (K) and sodium (Na) as biomarkers. METHODS A total of 2,124 men and 1,998 women 25 to 74 years of age with a 24-hour urine collection, a random sample of the Belgian Interuniversity Research on Nutrition and Health (BIRNH). were studied. Dietary intake (D), including alcohol consumption, was assessed by a one-day food record. Basal metabolic rate (BMR) was predicted from age, gender and weight. As a measure for the degree of reporting error, D-K/U-K, D-Na/U-Na, EI/U-K, Non-alcohol EI/U-Na (NAEI/U-Na), EI/U-Na, EI/U-creatinine and EI/BMR ratios were calculated and compared among non-, moderate and heavy drinkers in both genders. RESULTS EI, NAEI and all seven ratios examined generally increased with the level of alcohol intake in both genders. After adjustment for age, body mass index, smoking and educational level, most ratios were significantly higher in moderate drinkers (p < 0.02 to p < 0.0001) and in heavy drinkers (all p < 0.0001) than in non-drinkers. These differences were most significant in male heavy drinkers. The exceptions were D-K/U-K, D-Na/U-Na and NAEI/U-Na in moderate and female heavy drinkers and EI/U-K in male moderate drinkers. The estimated amount of the overreporting of EI by heavy drinkers was 27.8% in men and 13.7% in women. CONCLUSIONS This study provides evidence that EI and NAEI obtained from the BIRNH study was overreported among alcohol drinkers, especially among male heavy drinkers. It also indicates that EI from alcohol replaced EI from food.