In 11 insulin-dependent diabetic subjects, aged 12-32 yr, we evaluated the efficacy of dual, basal-rate pump delivery of insulin without preprandial boluses. Mean HbA1c fell from 11.6 +/- 3.1% to 7.7 +/- 1.8% at 30 days (P less than 0.005), and remained at 7.1 +/- 1.3% at the time of this evaluation (mean duration of therapy, 6.6 mo). These data suggest that dual-rate continuous basal insulin infusion is an effective means of achieving good diabetes control. Furthermore, it is simpler than the preprandial bolus approach currently used, which may make it suitable for more patients.