Background. The OPS imaging technique has been introduced for in vivo assessment of microcirculation in humans. The aim of this study was to validate the new technique against intravital fluorescence microscopy (IFM) for the visualization of colon microcirculation in a murine model of inflammatory bowel disease (IBD). Method. IBD was induced in Balb/c mice by dextran sulfate sodium, controls received normal water. In each animal, both the CYTOSCAN(TM) A/R and IFM were used to image the microcirculation (n = 7 in each group). The postcapillary venular diameter was analyzed on the colon muscularis and mucosa. Results: The venular diameter correlated significantly between both methods representing the good correspondence between both methods. Conclusion: Our study demonstrates that the new technique for visualization of microcirculation without use of fluorescent dyes, the OPS imaging, allows for quantitative measurement of a key microcirculatory parameters of the mouse colon. Copyright (C) 2002 S. Karger AG, Basel.