The aim of the study was to compare lispro (LP) and Insuman(R) (I) insulin in continuous subcutaneous insulin infusion (CSII) therapy with respect to blood glucose control as expressed by the standard deviation of blood glucose (SD(BG) ) and HbA(1c) and to monitor the well-being (WBQ) and treatment satisfaction (DTSQ) parameters during such treatment. Forty-one IDDM patients who had used CSII for at least 6 months participated in an open-label, randomized, cross-over, multicenter study for 4 months (2 months LP and 2 months I or vice versa). Boluses with LP were given 5 min before each meal and with I 30 min before each meal. During LP administration compared with I, the SD(BG) of all blood glucose values (3.6 mmol/l vs. 3.9 mmol/l, p=0.012), as well as the SD(BG) of the postprandial, blood glucose values (3.6 mmol/l vs. 4.0 mmol/l, p=0.006), were significantly reduced. The HbA(1c) was significantly lower during LP administration (7.4% vs. 7.6%, p=0.047). The incidence of hypoglycemic events per 30 days (capillary blood glucose<3.0 mmol/l and/or symptoms) did not significantly differ between LP and I (9.7 vs. 8.0 per month, p=0.23). The total amount of daily insulin was slightly but significantly lower with LP, compared to I (38.0 IU vs. 40.3 IU, p=0.004). There was no treatment effects of LP compared to I concerning WBQ and DTSQ. It is concluded that in CSII therapy LP is superior to I with respect to the stability of blood glucose control, a lower HbA(1c), a less insulin requirement without increasing the frequency of hypoglycemia.