Statins have antithrombotic actions. Human whole blood labeled with the lipophilic dye 3,3′-dihexyloxacarbocyanine iodide was treated with increasing concentrations of simvastatin (1-20 μM) or vehicle for 5 minutes and perfused through collagen-coated (400 μg mL⁻¹) Vena8 Biochips at a shear rate of 20 dyne/cm². Thrombi were recorded over a 10-minute period through a series of images in the Z-plane through their full depth using a Nikon Eclipse (TE2000-U) microscope, and thrombus fluorescence intensity was calculated using Slidebook, Version 5 (A). Numerical data represent sum fluorescence intensities, mean ± SD of 4 separate experiments (n = 4), P < .001 (nonparametric Kruskal-Wallis global) (B). In vivo thrombosis was assayed using a laser injury model by intravital microscopy. Fluvastatin (1-20 μM) or vehicle was administered intravenously to mice, and platelets were fluorescently labeled by injection of Alexa 488–conjugated anti-GPIb antibody. After laser-induced injury of the cremaster muscle arterioles, accumulation of platelets was assessed. Representative images of thrombi obtained from mice treated with or without fluvastatin (1 μM) at different time intervals are shown. Arrows indicate the direction of the blood flow (C). Median fluorescence intensity was measured from 21 thrombi from 4 mice from each of control and fluvastatin (1-20 μM)–treated groups (D-E). P values calculated by nonparametric Mann-Whitney test (P < .05).