Previous research has suggested that obesity is associated with increased high on-treatment platelet reactivity. We therefore tested platelet reactivity in 251 patients with VerifyNow P2Y12, vasodilator-stimulated phosphoprotein phosphorylation, and light transmission aggregometry with adenosine diphosphate 5 and 20 ΞΌM 6 to 24 hours after percutaneous coronary intervention. High on-treatment platelet reactivity was defined as a maximum platelet aggregation β₯46% for light transmission aggregometry with adenosine diphosphate 5 ΞΌM or β₯60% for 20 ΞΌM, platelet reactivity index β₯50% for vasodilator-stimulated phosphoprotein phosphorylation, and P2Y12 reaction units β₯235 for VerifyNow. The relation between body mass index (BMI) and platelet reactivity values was examined with Spearman coefficients; BMI and high on-treatment platelet reactivity were assessed with Student's t test. Multivariable logistic regression for high on-treatment platelet reactivity was also performed. Average BMI was 30.3 Β± 5.9 kg/mΒ² and 44% of patients had a BMI β₯30 kg/mΒ². Overall there was very poor correlation between BMI and on-treatment platelet reactivity, with Spearman coefficients ranging from 0.08 to 0.10. BMI was also not associated with the various definitions of high on-treatment platelet reactivity. Multivariable logistic regressions showed no association between BMI and high on-treatment platelet reactivity. In conclusion, and contrary to previous reports, we found no association whatsoever between BMI and on-treatment platelet reactivity as quantified by a variety of platelet function tests.