['We conducted a randomized study to compare the effect of direct stenting (DS) and conventional stenting (CS) on post-procedural index of microcirculatory resistance (IMR) values.', 'Direct stenting has been suggested to reduce periprocedural microcirculatory injury compared with stenting that follows pre-dilation (CS). The index of microcirculatory resistance is a sensitive invasive marker of coronary microvascular resistance.', 'Fifty patients admitted for elective percutaneous coronary intervention (PCI) were included. All patients had stable angina (Canadian Cardiovascular Society class <IV) related to a lesion suitable for DS and were randomized to DS (n = 25) or CS (n = 25). Baseline demographics and clinical and procedural data were comparable in both groups. An intracoronary pressure/temperature sensor-tipped guide wire was used. Thermodilution curves were obtained at baseline and during maximal hyperemia achieved by infusion of intravenous adenosine. The index of microcirculatory resistance was calculated from the ratio of the mean distal coronary pressure at maximal hyperemia to the inverse of mean hyperemic transit time.', 'After otherwise-uneventful PCI, patients treated with CS had significantly greater IMR (DS 13 +/- 3, CS 24 +/- 14; p < 0.01) and tended to have greater post-PCI troponin T values (DS 0.035 +/- 0.04, CS 0.17 +/- 0.02; p = 0.07). In the whole sample, 20% of patients had post-PCI troponin release (troponin T >0.03 ng/ml). Patients with troponin elevation had significantly greater post-PCI IMR values than patients without troponin elevation: 24.7 +/- 13.2 versus 16.9 +/- 10.2; p = 0.04.'] Is direct stenting for stable angina pectoris associated with reduced periprocedural microcirculatory injury compared with stenting after pre-dilation?