OBJECTIVE This study sought to evaluate the influence of intraaortic balloon pump (IABP) counterpulsation on the microcirculation in patients with cardiogenic shock (CS) complicating acute myocardial infarction. BACKGROUND In patients with shock profound alterations of the microcirculation have been observed and their clinical relevance has been described. Different treatment strategies exist to improve microvascular perfusion in patients with CS; however, the role of IABP treatment is not clearly defined. METHODS A predefined substudy of the randomized Intraaortic Balloon Pump in Cardiogenic Shock II trial (IABP-SHOCK II) investigated the sublingual microcirculation using a sidestream darkfield intravital microscope on days 1, 2 and 4 after the onset of shock. Perfused capillary (<20 µm, PCD) and vessel densities (<100 µm, PVD), total capillary (TCD) and vessel (TVD) densities were determined. In addition, the proportion of perfused vessels was assessed. RESULTS Forty-one patients were included in this substudy (n = 24 with IABP support vs. n = 17 without IABP support). No significant differences between treatment with or without IABP regarding PCD, PVD, TCD, TVD and the proportion of perfused vessels were evident on all three timepoints (p = n.s. for all). Microvascular perfusion showed inverse correlation with subsequent serum lactate levels (-0.366; p = 0.02) without being significantly correlated with lactate levels at the timepoint of the microcirculatory investigation. In Kaplan-Meier analysis microcirculatory parameters showed significant discrimination of prediction for time to death (p < 0.05 for all). CONCLUSIONS In patients with CS, there is no effect of IABP treatment on microvascular perfusion. Parameters of the microcirculation might be helpful to identify high risk patients.