The aim of this study was to investigate the impact of improved metabolic control on platelet reactivity in patients with type 2 diabetes undergoing percutaneous coronary intervention (PCI). Twenty-two patients were randomised to intensive insulin or conventional treatment for diabetes. Platelet P-selectin expression was analysed before and three months after PCI. Metabolic control, as measured by level of glycosylated haemoglobin (HbA1c) and platelet P-selectin expression, was similar in the two treatment groups after three months. However, six of the 12 patients in the intensive group had increased levels of HbA1c after three months and three patients of the 10 in the conventionally treated group showed improved metabolic control. A re-analysis was performed, based on metabolic control. It showed that patients with improved control at three months (HbA1c 6.1% +/- 0.7 at baseline; 5.7% +/- 0.5 at three months; p<0.01; n=9) had lower ADP-induced P-selectin expression (p<0.05) than patients with worsened glycaemic control (HbA1c 5.9% +/- 1.0 at baseline; 6.5% +/- 1.4 at three months; p<0.01; n=13). Levels of HbA1c and fasting glucose were correlated to P-selectin expression (R=0.34 and R=0.31; p<0.05). We conclude from this study that improved glycaemic control reduces platelet reactivity in type 2 diabetes patients following PCI.