Considerable interest has recently been focused on the computer as a new method to improve outpatient treatment of insulin dependent diabetics. Different ways of programming procedures have been proposed to simulate an experienced physician's capability to adjust insulin dosage in a mathematical form. We report here the results of a controlled study with a program for conventional insulin therapy in in- and outpatient treatment. Eleven inpatient type-I-diabetics could be well controlled after 8 days, and 6 outpatient treated type-I-diabetics improved all relevant metabolic parameters after 30 days compared to a control period of the same duration. So, computer assisted therapy promises to be a worthful aid in the treatment of diabetes.