Abstract: To determine if there is a progression from vasculogenic mimicry channels to mosaic vessels to endothelium- dependent vessels during melanoma tumor growth. Methods: C57 mice were inoculated with B16 melanoma cells and were sacrificed when the size of tumor tissue reached approximately 0.5 mm. All of the tumor tissues were sectioned. The density of vasculogenic mimicry channels, mosaic vessels and endothelium- dependent vessels was assessed for each of the sections using immunohistochemical double- staining and electron microscopy. The time trend of the three patterns of microcirculation was determined by the number of vessels. Results: With increasing tumor volume, the number of vasculogenic mimicry channels decreased and the number of endothelium- dependent vessels increased . The number of mosaic vessels showed no trend according to tumor size. The number of endothelium- dependent vessels showed a significant positive correlation to the size of the tumors (γ=0.718, P=0.009) and a distinct negative correlation to the number of VM channels (γ=0.77, P= 0.003). The walls of the mosaic vessels were composed of tumor cells and endothelial cells. Conclusions: In the early stage of tumor growth, vasculogenic mimicry is the main pattern of blood supply. With increased tumor size vasculogenic mimicry is replaced by endothelium- dependent vessels. Mosaic vessels may represent an intermediate stage between VMand endothelium- dependent vessels.