A comparison of 57 cases (in children with serum calcium concentration < 2.2 mmol/L) and 171 controls (in children with serum calcium level > or = 2.2 mmol/L) was carried out to assess whether the intake of at least 1.5 L/wk of soft drinks containing phosphoric acid is a risk factor for the development of hypocalcemia. A significant association was found: odds ratio = 5.27; 95% confidence interval, 3.17 to 8.75; p < 0.001. The hypothesis of a causal relationship between intake of phosphoric acid-containing soft drinks and hypocalcemia warrants further investigation.