Management of glucose homeostasis in newly kidney transplanted insulin-dependent diabetic patients is difficult. To examine whether continuous subcutaneous insulin infusion (CSII) could reverse this problem, six consecutive kidney-transplanted Type I diabetic patients either proceeded with conventional insulin therapy (CIT) or were changed to CSII beginning on the third postoperative day. After a mean of 13 days, the insulin administration mode was changed from CIT to CSII (n = 3) or from CSII to CIT (n = 3), and continued for a further 15 days. Mean blood glucose calculated on the basis of four daily measurements (8.00, 12.00, 17.00, 22.00 h) during the study periods was significantly lower during CSII (8.0 +/- 0.4 mmol/l, mean +/- SEM) than on CIT (11.0 +/- 0.6 mmol/l; p less than 0.005). Moreover, the variability of blood glucose expressed as the M-value was lower during the pump treatment compared to CIT (p less than 0.001), while the number of blood glucose values below 3.0 mmol/l was similar (3.8 vs. 4.4%). Diurnal metabolic and hormonal profiles were twice determined on each regimen with 2 hourly sampling. Glycemic control was again found to be improved during CSII therapy as compared to CIT (p less than 0.01 or 0.05 less than p less than 0.10). Moreover, insulin pump treatment resulted in a significant reduction of two major intermediary metabolites, lactate and glycerol (p less than 0.05 and p less than 0.01, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)