The incidence and magnitude of hypoglycemia (i.e., blood glucose values less than 50 mg/dl) were assessed by continuous blood glucose monitoring over 24 h in 10 insulin-dependent diabetic (IDD) patients treated with continuous subcutaneous insulin infusion (CSII) and 9 IDD patients under intensified conventional treatment (ICT). A newly developed, battery-powered blood glucose monitor was employed. Patients were thus enabled to move freely in the hospital premises. Despite similar quality of previous blood glucose control (HbA1: 8.0 +/- 0.05% CSII versus 8.0 +/- 0.3% ICT, mean +/- SEM), the obtained profiles showed better regulation under CSII treatment (mean blood glucose [MBG], 99.6 +/- 10.0 versus 133.1 +/- 7.4 mg/dl; M-value, 12.3 +/- 3.5 versus 26.2 +/- 4.1; mean amplitude of glycemic excursion [MAGE], 71.9 +/- 8.7 versus 132.9 +/- 14.2 mg/dl; CSII versus ICT, mean +/- SEM). The incidence of blood glucose values less than 50 mg/dl was 9/10 patients (CSII) and 5/9 patients (ICT). In both groups, hypoglycemia was most frequent at noon and was related to elevated pre- and postprandial free insulin levels. Patients became aware of hypoglycemia only in 6/23 episodes (CSII) and 6/8 episodes (ICT). Our data indicate that CSII as well as ICT may result in postprandial hyperinsulinemia leading to frequent hypoglycemic episodes of variable length, reassessing the traditional experience of close correlation between aggressive insulin therapy and enhanced hypoglycemic risk.