Microangiography is a very effective method in evaluating morphological changes of small vessels not onlybecause it shows subtle changes in microvasculature but also shows whole length of the vessels. Reccently manyexperimental studies on microagniography of normal and injured tissues are reported, but there's no report onmicroangiography of artificially induced cancer tissue. Authors artificially induced breast carinoma in rats withintravenous infusion of carcinogenic substance, N-methyl-N-Nitrosourea, and microangiography was done to evaluatevascularity and morphological changes of vessels of the cancer tissue. The results are as follows; 1.Distribtution of the tumor vessels showed tendency to form bolules. 2. Overall tumor vascularity was slightlyhypervascular. 3. Variable sized, parallell arraged, tumor vessels surrounded the boundary of the lobules whilemore small vessels invaginated to the center of lobules in tortuous or straight fashion. 4. In overall, peripherayof the lobule was more vascular than center. 5. There was no evidence of cental tumor necrosis, and findings ofextravasation of dye or venous lake formation were minimal. 6. Pathologically, the tumor tissue was welldifferentiated adenocarcinoma with tendency of lobule formation.