In 55 poorly controlled insulin-dependent diabetics, we tried to discover criteria for an improvement of metabolism by means of the "artificial beta-cell" (Biostator). To this end, during the first 24 h of hospitalization, blood glucose was monitored continuously under conventional insulin therapy (monitoring period). Insulin requirement was determined during the next 24 h by the artificial beta-cell (feedback period). Corrections of diabetes regimen were made with reference to the insulin consumption during the feedback period and to the extent of the postprandial blood sugar increases and decreases during the monitoring period. The resulting new diabetes regimen led to a significant improvement of the daily blood sugar profiles.