Although microsurgical techniques have been accepted routinely in many plastic surgical operations, many experimental studies are currently being conducted to refine the results. Most of these studies are difficult to perform and evaluate and the results are not always free of bias. Many scientific disciplines recently use the mathematics for simulation and modeling to predict the results of difficult experiments. Slit and hole end-to-side microanastomosis techniques are frequently preferred by many microsurgeons. Diamond technique recently proposed by the senior author is also a technique of end-to-side anastomosis with some advantages. The authors used mathematical simulation and modeling to compare two end-to-side microanastomosis techniques namely hole and diamond. The authors measured cross sectional areas of anastomosis in both techniques with different input data. The results showed that for end-to-side anastomosis, at angles less than 60 degrees, diamond technique yields a greater cross sectional area at anastomosis site compared with that of hole technique. (c) 2008 Wiley-Liss, Inc.