An artificial pancreas capable of maintaining blood sugar homeostasis within the physiological range is described in this paper. The blood sugar is continuously monitored and then interpreted by a minicomputer which in turn controls and implements the delivery of insulin (or glucose). The entire system is automatic and by giving insulin according to a projected blood sugar level the pattern of insulin administration is similar to the biphasic response of the normal pancreas. Five parameters for control can be selected and altered at will so that any level of normoglycemia can be maintained. Hypoglycemia is not encountered, and none of the patients experienced any side effects during or after the trials. The clinical trials involved a two-day study. On the first day the blood sugar profiles were monitored throughout the day. The patients were given their usual doses of subcutaneous insulin and ate measured meals and snacks. On the second day, they received no subcutaneous insulin; insulin was administered intravenously in accordance with the moment-to-moment requirements of the patients who were given meals the same as those of the previous day. Graphs plotted on a common time scale compare the blood sugar patterns on the two successive days and show the significant improvement in blood sugar homeostasis achieved by this artificial pancreas.