The chicken embryo's chorioallantoic membrane (CAM) is widely used as an in vivo model to study the vascular effects induced by agents administrated topically or intravenously. Hence, in the vascular plexus of this respiratory membrane, angiogenic and anti-angiogenic agents, as well as phototoxic effects have been studied. The main goal of this study was to characterize the capillary network of the CAM after topical administration of dimethyl sulfoxid (DMSO), a frequently used solvent of lipophylic drugs, including potent anti-VEGF agents. The CAM capillaries were observed between days 8 and 9 of the embryo development, with an epi-fluorescence microscope equipped with a sensitive camera by intravenous injection of a fluorescent agent and a non-fluorescing absorber (in the extra-embryonic cavity) to screen the tissue background fluorescence. The fluorescence images of the CAM vasculature were then processed in order to obtain a skeleton of the vessels and capillaries. This was done to quantify descriptors such as the number of branching points/mm 2, the mean area value of the vessels network meshes, and the mean of the 3 rd quartile of the histogram of these meshes, were then extracted. Our results demonstrate that the topical administration of an aqueous solution of 20 μl of DMSO at concentrations equal or larger than 0.1% turned out to modify the capillary network morphology in a dose-dependent manner as compared to the control (20 μl of 0.9% NaCl). © 2009 Copyright SPIE - The International Society for Optical Engineering.