Renal fibrin deposition does not correlate with renal failure or mortality. Renal fibrin deposition was quantified, following 24 hours' reperfusion after 25 minutes of renal ischemia or after sham surgery, by indirect immunofluorescence with an antifibrin/fibrinogen antibody detected with a FITC-labeled secondary antibody. Tissue sections (10 fields per slide, 400×) were viewed with an Olympus BX51 epifluorescence microscope equipped with a uPlanFl 40 ×/0.75 NA air objective, and digital images were captured with a Retiga EXi digital camera. To determine the area of fibrin staining, images were processed with SlideBook 4.0 for Macintosh (Intelligent Imaging, Denver, CO). Representative micrographs of (A) WT sham-operated, (B) WT, (C) low-TF, (D) C57BL6 hirudin-treated, and (E) PAR-1^−/− mice 24 hours after renal IR. Mean tubular score ± SEM indicated below each panel. (F) Quantitation of renal fibrin deposition 24 hours after renal IR from WT (n = 12), low-TF (n = 8), WT (n = 12) mice treated with hirudin, PAR-1^−/− (n = 12) mice, and sham-operated mice. WT and PAR-1^−/− mice undergoing IR had significantly more fibrin staining compared with sham-operated WT mice (*P < .001). Low-TF, and WT mice treated with hirudin had significantly reduced fibrin staining compared with WT mice after IR (**P < .001). Data are expressed as mean ± SEM.