The objective of this proposal is to demonstrate a viable, functionally integrated multivariable artificial pancreas (mvAP) that will address meal, physical activity (PA) and acute psychological stress (APS) challenges without any manual inputs to better regulate glucose levels of people with diabetes. Acute psychological stress and many other forms of PA besides planned exercise can affect blood glucose levels and cause challenges to maintaining euglycemia for people with type 1 diabetes mellitus (T1DM). Various PA and APS affect the metabolism and sensitivity to insulin in different ways. Hence, their types, intensities and durations, and their individual and concurrent presence must be detected in order to determine the optimal insulin administration. The mvAP approach provides a well-integrated and user-friendly technology with minimal burden on the user and mitigates the effects of unexpected PA and APS inducements. Twenty subjects with type 1 diabetes (ages 18-60) who use insulin pumps enrolled in this study. The study will take place at the UIC-College of Nursing Diabetes and Exercise Laboratory. The protocol will include 1 screening visit and 5 sessions at the laboratory. The primary activities at each meeting will include: (1) screening; (2) measurement of peak exercise capacity; (3) estimation of maximal strength from submaximal strength tests; (4) Trier Social Stress Test; (5) submaximal bouts of aerobic and resistance exercise, and activities of daily living with and without stress (e.g., mental calculations, video games). These activities will be included visit 3, 4 and 5 as appropriate. In addition, subjects will perform activities at home include: housekeeping chores, stationary bike (if available); treadmill (if available); walking; and light weights (if available). Periodically, the research assistant will call the subject during these times and ask them to perform stress-inducing activities while performing the activity. The stress inducing activities will include mental challenges such as a mathematical computation while performing the activity. The subjects will be called at home 3-5 times during the study. The fully automated algorithm will be tested in a home setting, however, the methodology will be developed and approved for testing later in the study.