Abstract We determined the serum levels and the dietary intake of Mg and Ca in 93 institutionalized elderly people (24 men and 69 women) in Granada (Spain). The serum samples had mean concentrations of 21.39 ± 2.08 mg/l magnesium and 93.39 ± 9.24 mg/l calcium. No significant differences were found in the serum levels of the two minerals as regards the sex of the subjects. Application of linear regression analysis to the serum Mg and Ca levels showed a statistically significant positive correlation ( P < 0.05). A low vitamin D intake of these subjects (51.8% of the recommended dietary allowance) was observed. The intakes of Ca and Mg correlated positively together, as well as with the intakes of energy, protein, fibre (in the case of Mg only), iron and phosphorus ( P < 0.05). The Ca and energy intake were adequate to their current recommendations, as too was the Ca:P ratio, whereas the diet had a poor supply of fibre, vitamin D and Mg.