To determine whether abnormalities of lipid and aminoacid metabolism observed in diabetes are corrected when plasma-glucose levels are restored to normal, eight insulin-dependent diabetics were treated for 7-14 days with a portable infusion pump which delivers insulin subcutaneously in basal (between-meal) doses with pulse-dose increments before meals. Mean plasma-glucose (206 +/- 24 mg/dl during conventional insulin treatment) fell to 89 +/- 3 mg/dl at day 7 and 84 +/- 2 mg/dl at day 14 of pump treatment; glycosuria was eliminated. Plasma cholesterol, triglycerides, and free fatty acids were elevated during conventional insulin treatment but fell to normal after 7 days of pump treatment. Plasma-levels of branched-chain aminoacids were 50-60% above control levels during conventional treatment but fell to normal after 7 days of pump therapy. Aminoacids were reduced from their high postprandial levels to normal values after insulin-pump treatment. In addition to restoring plasma-glucose to normal, treatment of diabetes with a portable insulin-infusion system results in restoration of normal lipid and aminoacid metabolism. Long-term use of this system may determine whether metabolic changes resulting from insulin lack cause the complications of diabetes.