We describe a method for electroporation-induced fusion of giant unilamellar vesicles (GUVs) with the plasma membrane of adherent cells. Using this method, the area of the cell membrane can be abruptly increased and various lipids can be introduced into the membrane. The process involves two steps: (1) the formation of GUVs with controlled membrane composition and (2) electrofusion of the GUVs to living cells using an electroporator for adherent cells. We demonstrate the technique on fish epithelial keratocytes and human foreskin fibroblasts, and discuss the influence of the composition of the GUVs on the fusion process.