A novel method of cell fusion is developed based on the fluid integrated circuit (FIC) concept, in which all cell handling components are photolithographically integrated on one substrate. A strong field constriction area is produced between the cell fusion electrodes by constricting all electric fluxes to a small opening made at the center of an insulating barrier placed between the electrodes. Cells are sent, one by one, from two micropumps, each containing a suspension of one type of cells, and then dielectrophoretically trapped at the opening to form a pearl-chain pair. Then the pulse voltage is applied to trigger the fusion of the cell pair. This procedure ensures that the fusion product is an exclusive one-to-one hybrid among the two species. As the cells are held at the opening without contact to the electrodes and, in addition, the membrane breakdown occurs only at the cell-to<ell contact, which i s located at the center of the opening where the field is strongest, the problems associated with the adhesion of the fusion product on the electrodes do not arise. The dimensions of the field constriction area made as small as cell diameters by the photolithography technique enable the application of constant pulse voltage on the cell membranes, regardless of the cell diameter. A l l those features enable a reliable and highly efficient cell fusions. The FIC cell fusion device i s constructed and its performance tested. Analysis of the field constriction area is also made.