A computer program was developed at Beth Israel Hospital in Boston to offer consultation to health care personnel treating patients with electrolyte and acid-base disorders, as the diagnosis of these disorders involves consideration of numerous factors and performance of tedious calculations. In order to obtain the necessary diagnostic information, the computer conducts a dialogue between itself and the person seeking its advice. The program then allows the computer to generate an evaluation note, which lists the diagnostic possibilities, explains the pathophysiology, recommends treatment, and provides references to the medical literature. The entire transaction, from data entry to printing, takes about 4 minutes. The computer program also compensates for entry of inconsistent data and for lack of data. Our experience with the program has revealed that it has favorably influenced patient care in a number of cases and has helped our staff better understand the pathophysiology and treatment of electrolyte and acid-base disorders.