Elderly patients are particularly sensitive to the development of various electrolyte abnormalities, since they commonly exhibit some derangements in the physiologic homeostasis of acid-base status and electrolyte balance. Our study was undertaken to assess the prevalence, as well as the pathophysiologic mechanisms involved in the development of electrolyte abnormalities in 248 elderly patients admitted to our clinic for a variety of causes. Fifty-five out of these patients (22.2%) had at least one electrolyte abnormality. In such cases a thorough laboratory investigation was performed in an attempt to delineate the pathophysiologic mechanisms involved in relation to age.