To assess the feasibility of preprogramming an open-loop device with insulin flow rates generated by the Biostator Glucose Controller, comparisons were made in 10 juvenile-onset diabetic patients between meals of equal size and composition taken in the morning, at noon, and in the evening and a bedtime snack during a 24-h period of Biostator glucose control. Four additional diabetic patients had Biostator glucose control for 72 h. Similar amounts of insulin were infused for the meals taken at differing times of the day and, except for the morning meal, for the same meal on two successive days. The meal-related glycemic patterns expressed as mean indices of meal excursions (MIME) were similar for meals of identical size and composition during a single day and for the same meal taken on two consecutive days. Preliminary results using an open-loop device preprogrammed by the Biostator system, although encouraging, underscore the deficiency of the subcutaneous route viz. the delayed entry of insulin into the circulation in achieving normal glucose levels and patterns.