Evaluation of therapeutic effects of transplanted cells in ischemic heart failure models are important issues. However, traditional injection needles that are widely used in clinical practice tend to reduce the amount of functional cells relative to the injected amount. We now describe a cell transplantation technique using a screw needle. After inducing acute myocardial infarction in a rat model, human embryonic stem cell-derived endothelial cells were injected into the infarcted regions with a screw or straight-curved needle. When an equal volume of cells was transplanted, the screw group suffered minimal cell loss, showed improvement in LV wall thickness (74.5 +/- A 6.2 vs. 64.4 +/- A 7.8 %), epicardium scar length (19.3 +/- A 2.8 vs. 24.6 +/- A 6.4 %), and area of engraft. Thus, even a simple change in the structure of an instrument can have a large impact on transplantation efficiency.