Recent advances in the techniques of molecular biology and cytogenetics have enabled the localization of several mutant genes which result in disorders of phosphate, calcium, magnesium and water homeostasis. Thus, the genes causing X-linked hypophosphataemic rickets, Lowe's syndrome, Di George syndrome, X-linked recessive hypoparathyroidism, multiple endocrine neoplasia Type I, primary hypomagnesaemia and X-linked nephrogenic diabetes insipidus have been mapped. The molecular and genetic studies which localized these disease genes are described and the implications of this gene mapping in genetic counselling and in further elucidation of the mineral metabolic defects are discussed.