AIM: To evaluate the potential advantages of a constant overnight subcutaneous delivery of insulin in type 2 diabetic patients who fail to achieve glycaemic control on oral antidiabetics. METHODS: Ten type 2 diabetic patients treated with oral antidiabetic drugs without gaining sufficient glycaemic control were included in this three-period study. All patients received continuous subcutaneous insulin infusion (CSII) with a short-acting insulin analogue, 2 IU/h, for 8 h during three consecutive nights (period A). Based upon the results from period A, two additional dose regimens of three nights (period B and C) were studied in random order. Serum insulin aspart, human insulin and plasma glucose (PG) profiles were recorded. RESULTS: In period A, fasting plasma glucose (FPG) was reduced from a mean +/- s.d. (mmol/l) value of 11.6 +/- 2.9 to 5.5 +/- 1.6 (p < 0.0001) during the first night. No additional lowering of FPG was seen the two succeeding nights. FPG narrowed as the range before the infusion was 7.3-15.2 mmol/l compared with 3.6-6.1 mmol/l on the last morning after infusion. The variability in PG profile during the first and the last night of CSII was small and not significantly different. The rising insulin aspart was mirrored by a decrease in human insulin. In period B and C, similar tendencies as for period A were seen. In period A, two patients each experienced one mild hypoglycaemic episode. CONCLUSIONS: CSII with an insulin analogue overnight effectively reduced FPG without occurrence of major hypoglycaemia in type 2 diabetic patients who fail to achieve glycaemic control on oral antidiabetic treatment.