The end‐to‐side anastomosis is frequently used in microvascular free flap transfer, but detailed rheological analyses are not available. The purpose of this study was to introduce a new modified end‐to‐side (Opened End‐to‐Side, OES‐) technique and compare the resulting flow pattern to a conventional technique. The new technique was based on a bi‐triangulated preparation of the branching‐vessel end, resulting in a “fish‐mouthed” opening. We performed two different types of end‐to‐side anastomoses in forty pig coronary arteries and produced one elastic, true‐to‐scale silicone rubber model of each anastomosis. Then we installed the transparent models in a circulatory experimental setup that simulated the physiological human blood flow. Flow velocity was measured with the one‐component Laser‐Doppler‐Anemometer system, recording flow axial and perpendicular to the model at four defined cross‐sections for seven heart cycles in each model. Maximal and minimal axial velocities ranged in the conventional model between 0.269 and −0.122 m/s and in the experimental model between 0.313 and −0.153 m/s. A less disturbed flow velocity distribution was seen in the experimental model distal to the anastomosis. The OES‐technique showed superior flow profiles distal to the anastomosis with minor tendencies of flow separation and represents a new alternative for end‐to‐side anastomosis. © 2013 Wiley Periodicals, Inc. Microsurgery 34:28–36, 2014.