The delayed subcutaneous insulin absorption makes stable blood glucose difficult to achieve in patients with type 1 diabetes, and there is a high risk for severe hypoglycemia. The human insulin analogs demonstrated to circumvent this major limitation of rapid-acting insulin particularly in the context of a continuous subcutaneous insulin infusion (CSII). As insulin profiles generated by implantable insulin pump (IP) are similar to lispro, we studied glucose profiles and the risk for severe hypoglycemia assessed by the low blood glucose index (LBGI) in a patient successively moved from CSII using regular-acting insulin to CSII using lispro and finally to an IP. Insulin delivery with the IP, and to a lesser extent CSII using lispro tend to reduce the average glycemia in comparison with CSII using regular-acting insulin (114.2+/-53.0, 131. 6+/-56.8 and 140.7+/-81.5 mg/dl, respectively). Reduction of glycemic fluctuations assessed by area under the curves was more pronounced during IP therapy in comparison with lispro and with rapid-acting insulin in CSII (789.5, 798.2 and 891.5 h.mg.dl-1, respectively). LBGI remained in the moderate range with IP and CSII using lispro (4.3+/-6.8 and 4.0+/-5.7 respectively), while LBGI was in the high range with rapid-acting insulin (5.5+/-10.2). In conclusion our case report suggests that IP tends to reduce the average glycemia and affect the amplitude of glycemic fluctuations in comparison with CSII using lispro, with an equivalent risk for severe hypoglycemia. A prospective randomized study is needed to compare these two modes of insulin replacement.