OBJECTIVE - To compare the safety and efficacy of insulin aspart (IAsp), buffered regular insulin (BR), and insulin lispro administered by continuous subcutaneous insulin infusion (CSII) in patients with type 1 diabetes. RESEARCH DESIGN AND METHODS - After completing a 4-week run-in period with BR, 146 adult patients with type 1 diabetes (with pretrial CSII experience) were randomly assigned (2:2:1) to CSII treatment with IAsp, BR, or lispro for 16 weeks in a multicenter, open-label, randomized, parallel-group study. Bolus insulin doses were administered 30 min before meals (BR) or immediately before meals (IAsp or lispro). RESULTS - Treatment groups had similar baseline HbA1c (7.3% ± 0.7 for IAsp, 7.5% ± 0.8 for BR, and 7.3% ± 0.7 for lispro). After 16 weeks of treatment, HbA1c values were relatively unchanged from baseline, and the mean changes in baseline HbA1c values were not significantly different between the three groups (0.00 ± 0.51, 0.15 ± 0.63, and 0.18 ± 0.84 for the IAsp, BR, and lispro groups, respectively). The rates of hypoglycemic episodes (blood glucose <50 mg/dl) per patient per month were similar (3.7, 4.8, and 4.4 for the IAsp, BR, and lispro groups, respectively). Clogs/blockages in pumps or infusion sets were infrequent; most subjects (76, 83, and 75% in the IAsp, BR, and lispro groups, respectively) had ≤1 clog or blockage per 4 weeks during the trial. CONCLUSIONS - Insulin aspart in CSII was as efficacious and well tolerated as BR and lispro and is a suitable insulin for continuous subcutaneous insulin infusion using external pumps.