With the advent of electronic computers that operate in the time-sharing mode, it has become possible to develop an automated system that can assist a physician in solving clinical problems. In the present study a teletype terminal has been linked to a time-sharing computer which has been programmed to evaluate clinical and laboratory information concerning patients with acid-base disorders. The program checks the data for evidence of internal consistency and requests additional information as needed to solve the acid-base aspects of the clinical problem. If sufficient information is provided, the program generates an evaluation note designed to review with the physician the pathophysiology of the disorder and to assist him in its management. If the input data are incomplete, the program draws the most useful conclusions possible based on the data provided, specifies the limitations which pertain to these conclusions, suggests further studies designed to circumvent these limitations, and while awaiting the results, suggests appropriate interim therapeutic measures. The time required to enter a patient's data and to print the evaluation note is approximately 4 min; the cost is comparable to that of many laboratory tests.