Unlabelled: Absorption rates of phosphate buffered insulin analogs aspart and lispro prevail over regular human insulin. However, insulin aspart has not been widely used. The aim of this open controlled clinical study is to compare the metabolic effects of insulin aspart and phosphate buffered insulin when both are used in insulin pumps according to the identical algorithms., Methods: Twenty one persons aged 39.9 +/- 2.89 (mean +/- SE) years (y) with type 1 diabetes mellitus duration of 17.9 +/- 2.21 y treated by an insulin pump for 4.3 +/- 0.53 y (at least 3 months), educated in self monitoring, entered the study. Mean plasma glucose, rates of hypo- and hyperglycaemias from the glucometer memory and other data from the first 256 +/- 19.97 days period with regular human insulin (check-up 1 and 2) and consequent 364 +/- 8.78 days long period with insulin aspart (check-up 3 and 4) were compared (paired t-test). Replacement of human regular insulin with insulin aspart after two check-ups was the only change in the treatment of diabetes. No special therapeutic education or training was made during the study., Results: In persons with type 1 diabetes treated by an insulin pump with insulin aspart, despite the lower daily dose of insulin aspart vs human regular insulin, the HbA1c decreased; the frequency of hypo- and hyperglycaemias and the BMI did not change., Conclusions: Insulin analog aspart appears to be more effective for continuous subcutaneous insulin infusion than regular human insulin.