The aim of this study was to estimate the dietary intake of calcium, magnesium and phosphorus in the elderly institutionalised population using duplicate diet sampling and to establish any related difference with the results obtained using food composition tables. The study was carried out on a sample group of 112 subjects in Granada (Spain). 1-week food duplicate samples offered by the elderly were studied. Calcium and magnesium were determined by AAS and phosphorus was determined by spectrophotometry. Anova showed significant differences (p<0.05) in all the minerals analyzed. These results suggest that the use of food composition tables is not suitable to evaluate the calcium, magnesium and phosphorus in nutritional trials. Moreover, the results show clearly that it is essential to consider these differences to establish the adequate intakes of calcium, magnesium and phosphorus for the elderly population in relation to the mineral bone status.