OBJECTIVE: To compare the results with continuous subcutaneous insulin infusion (CSII) versus multiple daily injections (MDI) of insulin in the treatment of type 1 diabetes during 18 months of follow-up. METHODS: We prospectively studied 29 patients with type 1 diabetes in Brazil; 17 patients elected to change from conventional insulin therapy (2 injections daily) (N = 3) or MDI (N = 14) to CSII therapy, and the other 12 continued to receive MDI therapy. All patients were treated with insulin lispro; patients in the MDI treatment group also received NPH insulin. We compared hemoglobin A1c (HbA1c) values, determined at baseline and every 3 months, between the two treatment groups. Other variables analyzed included weight, body mass index, total daily dose of insulin, and incidence of severe hypoglycemia. RESULTS: Patients in the CSII group had a significant decrease (P<0.001) in mean HbA1c at 18 months in comparison with baseline (8.3% versus 6.5%). In the MDI group, no significant changes were found in mean HbA1c. After 3 months of treatment, patients in the CSII group had a significantly lower mean HbA1c level than did patients receiving MDI (P<0.05). Of the 17 patients treated with CSII, all had HbA1c values less than 7.5% at 18 months, and 13 (76%) had HbA1c levels less than 7%. Although no significant variations in weight were observed in either group, the insulin/weight ratio decreased in the CSII group from baseline to 18 months (0.8 U/kg to 0.6 U/kg; P = 0.02). No episodes of severe hypoglycemia were noted in either group. CONCLUSION: Patients with diabetes treated with insulin lispro have better glycemic control with CSII than with MDI. Most of our patients in the CSII group were able to achieve target HbA1c levels less than 7% at 18 months without an increase in hypoglycemic episodes.