To improve understanding of the safety and efficacy of adding sitagliptin to treatment of patients with type 2 diabetes taking premixed insulin, data from patients using premixed insulin +/- metformin (screening HbA1c >= 7.5% and <= 11%) in either of two clinical trials in which sitagliptin 100 mg once-daily or placebo was added to various formulations of insulin treatment, were analysed. In both trials, insulin doses were to remain stable throughout the 24-week trial period. At week 24, the between-group difference (sitagliptin - placebo) in the least squares mean (95% confidence intervals) change from baseline in HbA1c in patients using premixed insulin was -0.43% (-0.58, -0.28), P <0.001. Adverse events were generally similar between the treatment groups. The incidence of symptomatic hypoglycaemia was slightly higher with sitagliptin, and the incidence of hypoglycaemia requiring medical attention was slightly higher with placebo; in both cases the difference was not statistically significant. The data from this pooled analysis confirm the utility of sitagliptin used in combination with premixed insulin in patients with type 2 diabetes.