This paper describes the phenomena of cell fusion: it’s importance in life processes and the use of electromagnetic field in induced electrofusion. Cell fusion is a common phenomenon in the living organisms during development and later for tissue regeneration. In living orga­nisms cell fusion is specific; regulated by different specialized fusion proteins and protein complexes. The ability of membranes to fuse nonspecifically, induced by an external influen­ce, such as an electric field is, however, important for biotechnology, medicine and research in biology. It enables us to produce very useful hybrid cells and their products – monoclo­nal antibodies, and to study basic mechanisms of cell fusion. Electrofusion is an efficient non viral and non chemical method for cell fusion, where cell membranes are destabilized by means of short, high voltage electric pulses. Optimal values of electrical parameters for fusion have to be determined for each cell line. Besides cell membrane destabilization, contact between cells should be achieved. In research, fusion yield is most often determined via fluorescent cell tracker dyes. In hybridoma technology selection media and appropriate mieloma cells are used, so that only hybrid cells survive. Hybridoma yield is, however, much smaller then fusion yield detected by means of fluorescent dyes since only fused cells that survive and proliferate are detected.