Investigation of 21 elderly women with a wide range of renal function showed that plasma creatinine concentrations above 100 μmol/1 were associated with glomerular filtration rates (GFR) below 50 ml/min. Plasma 1,25-dihydroxyvitamin D concentrations and radio-calcium absorption were directly related to GFR and were low when the GFR was less than 50 ml/min. Plasma parathyroid hormone concentrations were inversely related to GFR and were high when it was below 40 ml/min. In 126 women over the age of 60 admitted to a geriatric assessment ward, plasma creatinine concentrations above 100 μmol/1 were found in 73 and we conclude that renal impairment is common in elderly women admitted to hospital and is of sufficient degree to disturb the endocrine control of calcium metabolism seriously.