Serum calcium concentration was estimated, via a multichannel analyser, in all patients admitted to a 25 bed psychogeriatric inpatient unit and associated day hospital. Case notes of 629 consecutive admissions over a 42 month period were studied, and the prevalence of hypercalcaemia found to be 0.7 per cent, close to that estimated for the general population. Cases of hypercalcaemia with psychiatric symptoms, undetected medically because of vague and non-specific physical symptoms, do not appear in excess in a psychogeriatric population.